HY Neuro PDF - Stroke Risk Factors & Neuroanatomy

MEHLMANMEDICAL HY NEURO  MEHLMANMEDICAL.COM YouTube @mehlmanmedical Instagram @mehlman_medical MEHLMANMEDICAL.COM 2  MEHLMANMEDICAL.COM HY Neuro, by Dr Michael D Mehlman This PDF discus...

MEHLMANMEDICAL HY NEURO  MEHLMANMEDICAL.COM YouTube @mehlmanmedical Instagram @mehlman_medical MEHLMANMEDICAL.COM 2  MEHLMANMEDICAL.COM HY Neuro, by Dr Michael D Mehlman This PDF discusses with you HY diagnoses, risk factors, mechanisms, and even some neuro-related pharm. This PDF is not meant to be a 300-page textbook discussing nonsense that won’t show up on USMLE. I tell you exactly what you need to know for the exam without the superfluous garbage. I have a separate HY Neuroanatomy PDF where I go into detail regarding neuroanatomic structures showing cross-sections and labeled diagrams, etc. In this PDF, I do not do that. So if you need your hand held (i.e., “This is a pic of the brain. This is a pic of the spinal cord.” Etc.), the other HY Neuroanatomy PDF will hit many of those points for you. MEHLMANMEDICAL.COM 3  MEHLMANMEDICAL.COM Stroke risk factors - The two most important risk factors for stroke (cerebral infarction) on USMLE are hypertension and atrial fibrillation. - Regarding HTN, a strong systolic impulse pounds the carotid arteries, leading to endothelial damage and increased development of atherosclerotic plaques (carotid stenosis), which then launch off to the brain/eye. - Atrial fibrillation results in turbulence and stasis, leading to left atrial mural thrombus, which launches off. - Hypertension is most common in the population for causing stroke. Blood pressure control is more important than smoking cessation for decreasing stroke risk. - If the USMLE Q gives you a patient who has both AF and HTN, they want AF as the most important risk factor. In other words, even though HTN is the most common risk factor in the population for stroke, AF is still more likely to cause stroke if the patient has both. - There are other details regarding stroke I will discuss in this PDF, but for starters, these risk factors are pass-level points for understanding how/why most strokes occur – i.e., “How do most strokes occur?” à “Oh, well the patient will usually have carotid stenosis from HTN, where an atheromatous plaque has launched off, or will have AF where an LA mural thrombus has launched off.” Simple. - I discuss carotid stenosis and AF management for stroke prevention in detail in the HY Cardio PDF. Circle of Willis HY strokes Affected HY Points vessel - Anterior cerebral artery. ACA - Motor/sensory abnormalities of contralateral leg. - Middle cerebral artery. - Motor/sensory abnormalities of contralateral arm + face. MCA - Dominant MCA stroke (usually left) can lead to Wernicke or Broca aphasia (discussed below). - Non-dominant MCA stroke (usually right) can cause hemispatial neglect (inability to draw clockface). - Posterior cerebral artery. PCA - Contralateral homonymous hemianopsia with macular sparing. - Prosopagnosia (inability to recognize faces). Other stroke syndromes - Aka Wallenberg syndrome. - The answer for dysphagia + ipsilateral Horner syndrome after a stroke. - Due to stroke of posterior inferior cerebellar artery (PICA) or vertebral artery. Lateral medullary - PICAchew (Pikachu) à PICA stroke causes dysphagia. syndrome - Students might know Horner syndrome (ipsilateral miosis, partial ptosis, anhidrosis) can be caused by Pancoast tumor, but another HY cause is lateral medullary syndrome. Medial medullary - The answer for ipsilateral tongue deviation after a stroke. syndrome - Due to stroke of anterior spinal artery. - The answer for ipsilateral Bells palsy after a stroke. Lateral pontine - Due to stroke of anterior inferior cerebellar artery (AICA). syndrome - FACIAL (contains AICA backwards) à “That’s the one that’s Bells palsy.” - Midbrain stroke. Weber syndrome - The answer for ipsilateral CN III palsy (i.e., down and out eye) + contralateral spastic hemiparesis (weakness). - Basilar artery stroke. Locked-in syndrome - The answer for inability to move entire body except for eyes. Gerstmann - Stroke of angular gyrus of parietal lobe. syndrome MEHLMANMEDICAL.COM 4  MEHLMANMEDICAL.COM - Tetrad of 1) agraphia (inability to write); 2) acalculia (cannot do math); 3) finger agnosia (can’t identify fingers); 4) left-right disassociation (cannot differentiate between left and right sides of body). - Stroke of subthalamic nucleus. - Causes “ballistic” flailing of contralateral arm and/or leg. Hemiballismus - Weird condition, but for some reason asked. For example, if they say patient has random flailing of left arm following a stroke, answer = right subthalamic nucleus. Lenticulostriate strokes - HTN can cause lipohyalinosis (fancy word for microatheroma formation) of small lenticulostriate arteries deep within the brain. - Ischemia within these small vessels leads to necrosis and reabsorption of tissue, leading to tiny cavities called lacunae. - Unlike larger strokes, lacunar infarcts often do not present with cortical deficits like Lacunar infarcts aphasia, neglect, or visual field losses. Instead, they manifest as specific syndromes based on their location, such as pure motor hemiparesis, pure sensory stroke, ataxic hemiparesis. The USMLE doesn’t give a fuck about the specific types of lacunar deficits/strokes. They just what you to know they exist / are possible, and that the mechanism is HTN causing lipohyalinosis of these small, penetrating vessels, as mentioned above. - Charcot-Bouchard microaneurysms are tiny (40 degrees. - Abnormal convex curvature of thoracic spine. - Usually idiopathic due to old age; can be due to degenerative disc disease and Kyphosis compression fractures (osteoporosis). - If severe, can in theory cause restrictive lung disease due to impaired chest wall expansion. MEHLMANMEDICAL.COM 16  MEHLMANMEDICAL.COM MEHLMANMEDICAL.COM 17  MEHLMANMEDICAL.COM Lower limb reflexes / radiculopathies - The answer on USMLE if patient loses knee (patellar) reflex + has weakened knee extension. L4 radiculopathy - Pain / paresthesias / numbness in L4 distribution (anterior thigh + medial leg). - Disc herniation of L3-4. - Just remember that L4 is the one where the knee reflex is fucked up. - The answer on USMLE if patient loses dorsiflexion. L5 radiculopathy - Pain / paresthesias / numbness in L5 distribution (lateral + anterior leg). - Disc herniation of L4-L5. - The answer on USMLE if patient loses ankle (Achilles) reflex + has weakened plantar flexion. - Pain / paresthesias / numbness in S1 distribution (sole of foot + lower leg). S1 radiculopathy - Disc herniation of L5-S1. - Just remember that S1 is the one where the ankle reflex is fucked up. - SALT à S1, Achilles, Lateral leg dermatome, Tibial motor issue (plantar flexion). Lower limb nerve HY Points for USMLE - The answer on USMLE if patient loses both eversion and dorsiflexion of the foot. Common peroneal - Sensation to upper third of lateral leg (around and below lateral knee). (fibular) nerve - Splits into superficial and deep peroneal (fibular) nerves. - The answer on USMLE if patient loses only eversion of the foot, but dorsiflexion Superficial peroneal stays intact. nerve - Sensation to lower lateral leg and dorsum of foot. - The answer on USMLE if patient only loses dorsiflexion of the foot, but eversion stays intact. - Deep for Dorsiflexion, which means superficial is the one that does eversion instead. Deep peroneal nerve - Loss of dorsiflexion causes a high-steppage gait (patient has to lift foot high into the air with each step). - Also does sensation to webbing between 1st and 2nd toes. I’ve never seen NBME Qs ask or give a fuck about this sensation detail, but students get fanatical about it as if it’s supposed to be high-yield. - The answer on USMLE if patient loses plantarflexion of the foot (can’t stand on Tibial nerve tippytoes). - Sensation to bottom of foot / heel. - The answer on USMLE if patient has motor dysfunction of tibial and common peroneal nerves at the same time, or has sciatica (shooting pain down leg). - Splits into the common peroneal nerve and tibial nerve. - Does not supply sensation to thigh; sensation encompasses that supplied by the combination of the common peroneal nerve and tibial nerves. Sciatic nerve - Supplies some motor function to muscles of thigh but USMLE doesn’t care. - Sciatica = shooting pain from the lower back down the leg usually as the result of disc herniation; 2CK Neuro forms simply want NSAIDs as treatment; straight- leg test is classically used in part to diagnose, but I’ve seen this test show up on NBME material for simple lumbosacral strain (i.e., the test is non-specific and not reliable). - The answer on USMLE if patient has inability to adduct the hip with loss of Obturator nerve sensation to medial thigh. - The answer on USMLE if patient cannot extend knee and/or has buckling at the knee. Femoral nerve - Also does sensation to anterior thigh + medial leg (not thigh), although I haven’t seen sensation specifically asked for femoral nerve. - The answer on USMLE if patient loses sensation to medial leg. Saphenous nerve - Pure sensory branch of the femoral nerve. MEHLMANMEDICAL.COM 18  MEHLMANMEDICAL.COM - The answer on USMLE if patient loses sensation to lower lateral leg. In contrast, if sensation loss is upper lateral leg, that’s common peroneal nerve instead. Sural nerve - Often confused with saphenous. Good way to remember is: Sural is Lateral, therefore saphenous must be the one that’s medial. - The answer on USMLE if patient has Trendelenburg gait à opposite side of pelvis will fall while walking, so patient will tilt trunk toward side of lesion while Superior gluteal nerve walking to maintain level pelvis. - Innervates gluteus medius and minimus. - The answer on USMLE if patient cannot squat, stand up from a chair, or go Inferior gluteal nerve up/down stairs. - Innervates gluteus maximus. Neurogenic joint - Aka Charcot joint, where patient injures joint due to lack of joint sensation from peripheral neuropathy. - Usually seen in diabetes; can also be seen in neurosyphilis. - The answer on USMLE when they say diabetic patient has “disorganization of the tarsometatarsal joints” on foot x-ray. Upper limb nerve HY Points for USMLE - Main innervation of the deltoid, allowing for abduction of arm 15-90 degrees. USMLE wants you to know deltoid has an origin on the lateral clavicle and axillary nerve innervating it is at C5/C6. Axillary - Palsy caused by surgical neck of humerus fracture. - USMLE vignette will often say “flattened deltoid” or “loss of sensation over lateral upper arm / deltoid.” - Main innervation is lateral “3 and a half” fingers / thenar pad, and lateral forearm. - Does thumb abduction. (In contrast, ulnar nerve does thumb adduction) - NBME wants “palmar cutaneous branch of median nerve” as answer for sensation over thenar region. - Palsy caused by supracondylar fracture of humerus, or “distal shaft fracture.” Former is buzzy; latter sounds non-specific, but I’ve seen it this way on NBME. - Entrapment of median nerve causes carpal tunnel syndrome; will present as paresthesia/numbness of lateral hand / thenar region; can be caused by Median hypothyroidism (GAG deposition), acromegaly (growth of tendons), and pregnancy (edema); can occur bilaterally in construction workers using jackhammer. - Tx for carpal tunnel ultra-HY on 2CK FM forms. “Use of wrist pad when using computer” is answer on new 2CK NBME. If not listed, “wrist splint” is answer on FM form. If vignette says wrist splint fails, NSAIDs are wrong answer and not proven. USMLE wants “triamcinolone injection into carpal tunnel” (not IV steroids) as next answer. Surgery is always wrong answer for carpal tunnel on USMLE. - 2CK wants “electrophysiological testing” and “electromyography and nerve conduction studies” as next best step in diagnosis for carpal tunnel. - Main innervation of medial “1 and a half” fingers, and medial forearm. - Ulnar nerve also does finger abduction and adduction (i.e., interosseous muscles). - USMLE loves Froment sign for ulnar nerve injury, which is inability to pinch a piece of paper between the thumb and index finger (ulnar nerve needed for thumb Ulnar adduction against index finger, despite thumb being most lateral digit). - Distal compression (i.e., of wrist and hand only, not forearm) is aka Guyon canal syndrome and is caused by hook of hamate fracture; this can sometimes be seen in cyclists due to handlebar compression; presents as paresthesias / numbness of 4th and 5th fingers + hypothenar eminence. MEHLMANMEDICAL.COM 19  MEHLMANMEDICAL.COM - Proximal compression (i.e., medial forearm + wrist/hand) is aka cubital tunnel syndrome and is one of the most underrated diagnoses on USMLE, since its yieldness, especially on 2CK, is comparable to carpal tunnel syndrome, but students often haven’t heard of it. Essentially, patient will get paresthesias of medial forearm + hand, where it “sounds like carpal tunnel but on the ulnar side instead” à answer = cubital tunnel syndrome. - Tx for cubital tunnel syndrome is “overnight elbow splint.” Surgery is wrong answer on USMLE. - Main innervation for finger, wrist, and elbow extension. - Innervates BEST à Brachioradialis, Extensors, Supinator, Triceps. - Palsy occurs as a result of midshaft fracture of the humerus, or as a result of fracture at the radial groove (latter is obvious). Radial - Retired Step 1 NBME Q says construction worker sustains “comminuted spiral fracture of humerus” (unusual, since spiral fracture classically = child abuse), and they ask for the resulting defect à answer = “loss of radial nerve function.” - Highest yield point is that injury results in pronated forearm + wrist drop. - Main innervation of the biceps. - Just need to know injury results in loss of sensation over lateral forearm + Musculocutaneous decreased biceps function. - USMLE doesn’t give a fuck about what kind of injury causes palsy. Mononeuritis multiplex - Weird neuropathy that means neuropathy of “one large nerve in many locations” – e.g., wrist drop + foot drop in same patient. - Presents in patients with one of the vasculitides (i.e., Wegener, Churg-Strauss, microscopic polyangiitis). - In other words, you’ll get a vignette of Wegener, and then you’re like, “Wait, why does he/she have wrist drop though?” That’s just mononeuritis multiplex. - Formerly known as Wegener granulomatosis. - Answer on USMLE for adult with triad of 1) hematuria, 2) hemoptysis, and 3) “head-itis” – i.e., any problem with the head, such as nasal septal perforation, Granulomatosis with mastoiditis, sinusitis, otitis. polyangiitis - Associated with cANCA and anti-proteinase 3 (anti-PR3) antibodies. - Causes “necrotizing glomerulonephritis” that can lead to rapidly progressive glomerulonephritis (RPGN). - Formerly known as Churg-Strauss. Eosinophilic - Presents as combo of asthma + eosinophilia +/- head-itis. granulomatosis with - Head-itis always seen in Wegener vignettes, but maybe only ~50% of CS Qs. polyangiitis - Renal involvement rare for CS. - Associated with pANCA and anti-myeloperoxidase (anti-MPO) antibodies. - Will just present as hematuria in a patient who is pANCA / anti-MPO (+). Microscopic polyangiitis - Similar to Wegener, can cause RPGN. Hydrocephalus - CSF can flow freely between the ventricles and subarachnoid space around the brain and spinal cord. Communicating - The answer for meningitis causing hydrocephalus, where the mechanism is “failure of CSF reabsorption by the arachnoid granulations.” - Aka obstructive hydrocephalus. - When there is a blockage preventing flow of CSF between the ventricles or Non-communicating subarachnoid space. - There is an NBME Q where they give a tumor of the spinal cord in the setting of hydrocephalus, and the answer is obstructive hydrocephalus. MEHLMANMEDICAL.COM 20  MEHLMANMEDICAL.COM - Can be caused by aqueductal stenosis (narrowing of the cerebral aqueduct of Sylvius between the 3rd and 4th ventricles), which is the most common cause of congenital hydrocephalus. - Can be caused by colloid cyst, which is a benign fluid-filled growth at the anterior roof of the third ventricle, just posterior to the foramen of Monro. - Normal pressure hydrocephalus. - “Wet, wobbly, wacky” +/- Parkinsonism. - In other words: urinary incontinence, ataxia, and cognitive dysfunction. NPH - Due to impingement on the corona radiata (asked on an NBME), which is a white- matter bundle that connects the motor cortex superiorly to the internal capsule inferiorly. - Mechanism for urinary incontinence = “failure to inhibit the voiding reflex.” - Aqueductal stenosis is most common cause. - Most important cause on NBME, in my opinion however, is congenital Congenital toxoplasmosis, which presents as a triad of 1) hydrocephalus, 2) chorioretinitis, and 3) intracranial calcifications. - Appearance of enlarged lateral ventricles on imaging without true hydrocephalus. - Can be caused by loss of surrounding brain matter. Ex-vacuo - Alzheimer and schizophrenia are important causes on USMLE, where enlargement of the lateral ventricles is a finding that can sometimes show up in question stems. HY dementia types - Gradual-onset idiopathic cognitive decline. - Patient must have normal neurologic exam (i.e., no motor or sensory abnormalities). - MMSE score will be low (i.e., low-20s out of 30) on USMLE. If the diagnosis is instead benign senility, USMLE will give MMSE usually 28+. - Beta-amyloid plaques and neurofibrillary tangles (hyperphosphorylated tau protein) seen on brain biopsy. - Early-onset Alzheimer in Down syndrome (amyloid precursor protein gene is Alzheimer located on chromosome 21). - Presenilin gene mutations can cause Alzheimer (on NBME exam). Presenilin is a protein involved in the cleavage of amyloid. - Tx = cholinesterase inhibitors (donepezil, galantamine, rivastigmine); memantine (NMDA glutamate receptor antagonist) can also be used. - Sundowning is worsening of dementia at night that can resemble delirium. - 1st-line Tx for sundowning on NBME is “decrease ambient noise and distractions.” “Bright illumination of the room at all times” is wrong answer. - Aka Pick disease. - Presents usually as triad of 1) personality change, 2) apathy, and 3) disinhibition. Frontotemporal - Accumulation of hyperphosphorylated tau protein (similar to Alzheimer), except dementia rather than accumulating as neurofibrillary tangles, it accumulates as round, silver- staining inclusions knowns as Pick bodies. - Dementia + visual hallucinations + Parkinsonism. - Lewy bodies are collections of alpha-synuclein. This protein is deposited Lewy body dementia throughout the brain in Lewy-body dementia. In Parkinson disease, in contrast, it is deposited primarily in the substantia nigra pars compacta of the midbrain. - Aka multi-infarct dementia. - The answer for dementia + motor/sensory abnormalities. - Seen in patients who have repeated mini-strokes (cerebral infracts) due to Vascular dementia hypertension. - Resources tend to focus on this notion of “step-wise decline” (i.e., concrete timepoints at which deficits started), but it’s to my observation on NBME exams that this is rarely a salient aspect of Qs. What USMLE likes is giving motor and/or MEHLMANMEDICAL.COM 21  MEHLMANMEDICAL.COM sensory deficits – i.e., you’ll get a big paragraph with dementia, and you’ll notice somewhere in the stem that the patient has, e.g., 3/5 strength in the right upper extremity. This indicates Hx of stroke. - Just be aware AIDS can cause dementia, known as AIDS complex dementia. AIDS - Can present as “wet, wobbly, wacky,” similar to normal pressure hydrocephalus. - Not actual dementia. This is depression that presents as cognitive decline. - Patients with depression who have apathy will perform poorly on the MMSE. - The Q might say the patient is unable to draw a clockface, but when prompted, is Pseudodementia able to finish it quickly. They might also say patient remembers 0 out of 3 objects after 5 minutes. - Look for obvious signs of depression, such as short, quiet answers, and low mood. - The fancy name for neurologic degeneration seen in B12 deficiency. - Can present sometimes as a reversible cause of dementia. In elderly patients on tea and toast diets, or those in high-risk groups (i.e., vegans, pernicious anemia), Subacute combined B12 must be considered as cause of cognitive decline. degeneration - The patient can have peripheral neuropathy as a result of deficits to the 1) corticospinal tracts, 2) dorsal columns, and 3) spinocerebellar tracts. - The easy way to remember those three is to start by saying, “The spinothalamic tract is not involved.” Then you say, “Well what are other ones I can think of?” - Just be aware that neurosyphilis is a reversible cause of dementia and should be Neurosyphilis considered. There’s an NBME Q floating around for 2CK where they give (+) VDRL in 82-year-old woman with cognitive decline, and the treatment is penicillin. Parkinson disease / Parkinson-plus disorders - A Parkinson-plus disorder is a disease that presents similarly to Parkinson disease, but it’s not. - Loss of dopamine-secreting neurons in the pars compacta of the midbrain, with deposition of alpha-synuclein on biopsy. - Presents with classic features of bradykinesia/akinesia, resting tremor, shuffling, short-steppage gait, micrographia, and cogwheel rigidity. - Alpha-synuclein gene mutation most common; many genes implicated. - Carbidopa-levodopa is combo frequently used for Tx. Levodopa crosses the BBB to be converted to dopamine centrally. However, levodopa is subject to fast metabolism when administered alone. The addition of carbidopa functions as a competitive inhibitor of breakdown enzymes, resulting in increased levodopa availability for passage across the BBB. Do not confuse this mechanism with direct COMT inhibitors (tolcapone, entacapone), which prevent breakdown of L-dopa. Parkinson disease - Carbidopa-levodopa can cause psychosis if administered in too-high a dose. This is assessed on 2CK Psych forms, where if patient gets psychotic episodes following recent addition of C-L to regimen, or following an increase in dose, the answer is simply “decrease dose of carbidopa-levodopa.” “Discontinue carbidopa-levodopa is the wrong answer.” - Be aware of D2 agonist names – i.e., ropinirole, pramipexole, cabergoline, pergolide, and bromocriptine, which can all in theory be used as treatments. - Amantadine increases presynaptic release of dopamine. - Selegiline inhibits monoamine oxidase B, which is an enzyme that preferentially breaks down dopamine. USMLE wants you to know this can cause serotonin syndrome, either alone, or in combo with drugs like St John Wort or SSRIs. - Restless leg syndrome. - Idiopathic, irresistible urge to move legs while in bed/sleeping. - Most common cause is iron deficiency anemia. First step is checking the patient’s RLS serum iron and ferritin. - If iron studies are normal, gabapentin and D2 agonists (ropinirole, pramipexole) can be used. MEHLMANMEDICAL.COM 22  MEHLMANMEDICAL.COM - USMLE wants you to know that patients with RLS have increased risk of developing Parkinson disease, which makes sense since D2 agonists help, indicating a potential problem with dopamine signaling or production in some patients. - As discussed earlier, normal pressure hydrocephalus presents as “wet, wobbly, wacky” +/- Parkinsonism. - The parkinsonism is the most overlooked detail by students, who will usually only know the wet, wobbly, wacky part. - What the USMLE will do is give you an older male who has WWW triad + they give NPH you 2-3 more sentences describing what sounds like Parkinson disease, where you’re like “What the hell? Is this Parkinson disease?” No. It’s just NPH, which is a Parkinson-plus disorder, where it can look like Parkinson disease but it ain’t. - Once again, due to impingement on the corona radiata, and the mechanism they want for urinary incontinence = “failure to inhibit the voiding reflex.” - Parkinsonism in a young patient is Wilson disease till proven otherwise. - Excessive copper accumulation in tissues, including the basal ganglia and liver, due Wilson disease to inability to excrete it into bile. - I discuss this stuff in more detail in the HY Gastro PDF. - As discussed before, this is a Parkinson-plus disorder. Lewy body dementia - The patient will have dementia + visual hallucinations + Parkinsonism. - Obscure condition that gets asked on 2CK. - You just need to know that 100% of questions will say “axial dystonia + Progressive Parkinsonism,” where they’ll just ask for diagnosis straight-up. supranuclear palsy - Axial dystonia is a type of muscle condition resulting in abnormal posture and movement of the spine and torso. - Aka synthetic heroin. MPTP - Just know it is a cause of Parkinsonism. - Shows up on a 2CK Psych form. Students are like wtf? Optic neuritis - Inflammation of CN II (optic nerve) that presents variably as change in visual acuity, color vision, central scotoma, etc., and is basically always seen in multiple sclerosis on USMLE. I discuss MS more later. - Causes Marcus Gunn pupil (aka relative afferent pupillary defect). In this case, the intensity of light is under-sensed by the affected eye (afferent signal), so the resultant efferent CN III (oculomotor) parasympathetic output (back to the eyes for pupillary constriction) is attenuated; this means when you shine a light in the affected eye, both pupils constrict less in comparison to when the light is shone in the unaffected eye; this gives the mere impression that the pupils dilate when light is shone in the affected eye. Still confusing? Take a look at the following illustration (assuming a lesion of the patient’s right eye [left side of illustration]): MEHLMANMEDICAL.COM 23  MEHLMANMEDICAL.COM MEHLMANMEDICAL.COM 24  MEHLMANMEDICAL.COM MLF syndrome - Medial longitudinal fasciculus syndrome (MLF syndrome; aka internuclear ophthalmoplegia; INO). - Pathognomonic for multiple sclerosis. MS patients can also get optic neuritis (as mentioned above), but this is not pathognomonic for MS (i.e., it can be seen in other circumstances, such as with ethambutol or sildenafil use). - Mechanism for pathology: when you look to one side (let’s say the right), CN VI on the right and CN III on the left are activated. This unison of activation is accomplished when the left MLF in the midbrain is activated. In the case of MLF syndrome, the right eye can abduct without a problem, but the left eye will fail to adduct, and the right eye will exhibit nystagmus back toward the midline. - What you need to remember is: in INO, the side that cannot adduct is the side that’s fucked up. So if you look to the right and the left eye doesn’t adduct, then the left MLF is where the lesion is. Autoimmune neuropathies - T-cell-mediated attack against oligodendrocytes and myelin-basic protein. - Idiopathic autoimmune disorder classically in white women 20s-30s who live far from the equator. - Relapsing-remitting type is most common, where the patient will have repeated episodes of neurologic disturbances over many years at varying intervals. - Highest yield findings are optic neuritis and INO, as discussed above. Multiple sclerosis - Urge incontinence is exceedingly HY. Some students ask about overflow incontinence due to MS; I’ve never seen this on NBME. Urge incontinence is what shows up all over the NBME forms for MS. I discuss the incontinences in extensive detail in my HY Renal and Repro/Obgyn PDFs. - MRI is gold standard for diagnosis, showing scattered white matter lesions within the CNS (i.e., both brain and spinal cord). - CSF analysis shows IgG oligoclonal bands. MEHLMANMEDICAL.COM 25  MEHLMANMEDICAL.COM - Clonus and (+) Babinski sign (UMN findings) also HY. - Tx is steroids for acute flares (IV methylprednisolone). - b-interferon is what USMLE wants between flares to decrease recurrences. - Baclofen (GABA-B receptor agonist) is used for spasticity. - Aka Devic disease. - Sounds exactly like MS but they will say CSF oligoclonal bands are negative, and Neuromyelitis optica then the answer is just “antibodies against aquaporin-4.” - You say Wtf? Not my opinion. It’s asked on a 2CK Neuro form. - Amyotrophic lateral sclerosis. - In ALS, the lateral corticospinal tracts (UMN) and anterior horns (LMN) degenerate. - There are two things you will see in all ALS Qs, making the Dx very easy: 1) The vignette will always have combination of UMN and LMN findings. Fasciculations, decreased reflexes, decreased tone, and muscle atrophy are classic for LMN. Babinski reflex, clonus, increased (brisk) reflexes, increased tone are classic for UMN. Serum CK can be elevated due to increased tone. ALS 2) Must have no sensory findings. If any sensory abnormalities (i.e., paresthesias, numbness, etc.) are present in the vignette, ALS is the wrong answer. USMLE will often give vignette of ALS and then the answer is simply “motor neurons.” - Knowing this second point in particular will help on difficult 2CK Qs, where you’ll get a big paragraph + they say somewhere in the stem something about a sensory abnormality, and you can say, “Cool, not ALS.” For 2CK, next best step in Dx = “electromyography and nerve conduction studies.” - Guillain-Barre syndrome (aka acute inflammatory demyelinating polyneuropathy). - T-cell- and antibody-mediated destruction of Schwann cells and myelin of peripheral nerves. - In other words, MS = CNS/oligodendrocytes; GBS = PNS/Schwann cells. - Can be described as “segmental and inflammatory demyelination.” - Presents as ascending paralysis and loss of deep tendon reflexes. - Can affect both upper and lower limbs. GBS - Symptoms can start as tingling in the hands and/or feet. - USMLE can say “weakness of proximal and distal muscles in lower limbs and weakness of distal muscles in upper limbs” à the implication is that the weakness has already ascended in the legs but not yet in the arms. - Textbook cause is Campylobacter jejuni, but in almost all Qs they will not give a patient who has bloody diarrhea after a BBQ. In other words, you can’t use this as a crutch. They will just give you the symptoms alone and you have to know it’s GBS. - Chronic inflammatory demyelinating polyneuropathy. - Vignette will sound exactly like GBS, but symptoms will be present for months and progress slowly. CIDP - GBS, in contrast, develops quickly over days and peaks within weeks. - In other words, if you get a vignette where it sounds like GBS, but they say the symptoms have been present for 4 months, that’s CIDP, not GBS. There’s one Q on a 2CK form on it. - Charcot-Marie-Tooth disease. CMTD - Obscure peripheral nerve autoimmune disease that is the answer on USMLE if they give you high-arched feet (pes cavus), hammer toes, and foot drop. - LMN lesion of CN VII (facial nerve). - Paralysis of ipsilateral facial muscles. - Usually idiopathic/autoimmune following viral infection, shingles (i.e., Ramsay- Hunt syndrome II), or Lyme disease. Bell’s palsy - If the Q gives you Bell’s palsy and asks for next best step, the answer is do serology for Lyme disease. If this isn’t listed (or the patient doesn’t live in endemic area, such as Africa), choose “no further diagnostic studies indicated.” Nerve conduction studies are wrong (this is on NBME). Bell’s palsy is a clinical diagnosis. MEHLMANMEDICAL.COM 26  MEHLMANMEDICAL.COM - IV steroids, followed by a 10-21-day taper of oral steroids is indicated to minimize the immune response. - Ipsilateral hyperacusis (due to paralysis of stapedius muscle) and/or loss of taste to the anterior 2/3 of the tongue are basically nonexistent in questions. - There is a Q on NBME where they say patient has loss of taste following trauma + neurologic exam shows no abnormalities à answer = olfactory nerve (CN I) palsy, not CN VII, due to cribriform plate fracture (loss of smell means loss of most taste). If the Q wanted CN VII lesion, they would give a concurrent Bell’s palsy presumably, since loss of taste wouldn’t happen in isolation with CN VII palsy. - In contrast to CN VII lesion that is 19 times out of 20 LMN causing Bell’s palsy, you should be aware that 1/20 are UMN, which results in loss of motor function of the contralateral middle and lower face, with the forehead spared. - Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococci. - In rare cases, Group A Strep pharyngitis can cause a tic disorder, OCD, or ADHD in the weeks following infection. PANDAS - USMLE will give you kid who had sore throat two weeks ago + now has a new- onset tic, ADHD, or OCD, and they will ask what will most likely diagnose etiology for the disorder à answer = “anti-streptolysin O titers.” - Autoimmune movement disorder seen as part of rheumatic fever. - Chorea = fast, purposeless, jerky movements. Sydenham chorea - Vignette will give child who has rheumatic fever and then ask about the cause of the movement disorder, and the answer is just “autoimmune.” - I discuss rheumatic heart disease in detail in the HY Cardio PDF. Myoneural junction disorders - Autoantibodies against post-synaptic nicotinic acetylcholine receptors. - Classic vignette is female office worker in her 40s who has triad of 1) diplopia, 2) dysphagia, and 3) ptosis that worsens throughout the day. - Gets worse with recurrent stimulation of muscle (vignette might say the patient cannot perform upward gaze for 60 seconds). - Tensilon test is administration of edrophonium (short-acting acetylcholinesterase Myasthenia gravis inhibitor) à patient experiences significant improvement in symptoms. - Tx = pyridostigmine (longer-acting acetylcholinesterase inhibitor). - MG can be a paraneoplastic syndrome of thymoma. - 10-15% of patients with MG have thymoma. - If MG is diagnosed, a chest x-ray should be performed to look for thymoma. If the x-ray is abnormal, a CT scan is ordered. - Removal of the thymoma in these patients can significantly improve/cure the MG. - Autoantibodies against pre-synaptic voltage-gated calcium channels. - Presents as proximal muscle weakness that improves with activity (vignette might Lambert-Eaton say the patient tries to get up from a chair a few times before finally being able to). - Tensilon test does not significantly improve Sx in comparison to MG. - Highest-yield point is that it is a paraneoplastic syndrome of small cell lung cancer. Vertigo - Benign paroxysmal positional vertigo. - Vertigo is the feeling of the room spinning. - Brief episodes of dizziness, usually 30-60 seconds, sometimes with vomiting. - Caused by a semicircular canal otolith (ear stone; aka otoconia). - Otoconia made of calcium carbonate are normally found within the utricle and BPPV saccule of the inner ear and play a role in detecting acceleration and motion. If one becomes dislodged and enters the semicircular canals, BPPV results. - Diagnosis is made via Dix-Hallpike maneuver. In this test, nystagmus is induced when the patient is rapidly moved from a seated position to lying down with the head tilted backward and turned to one side. If nystagmus occurs, Dx = BPPV. MEHLMANMEDICAL.COM 27  MEHLMANMEDICAL.COM - Tx is Epley maneuver, which is a series of head movements aimed at moving the semicircular canal otolith back to the utricle, thereby curing the BPPV. - Viral infection + vertigo. Vestibular neuritis - Inflammation of the vestibular nerve (branch of CN VIII, vestibulocochlear nerve). - Viral infection + vertigo +/- tinnitus. - Inflammation of both the vestibular nerve and cochlear nerve. - This distinction of “VN is just vertigo whereas labyrinthitis is also tinnitus” is perpetuated on the internet, but I can tell you there is an NBME Q for Step 1 (that is repeated across forms) where they don’t mention anything about tinnitus and the answer is labyrinthitis (where vestibular neuritis isn’t listed). This is why I write “+/-“ for tinnitus above. Labyrinthitis - The tympanic light reflex can be abnormal, which can reflect increased middle ear pressure (sometimes seen with viral infection). I’ve seen the NBME write in the stem “abnormal light reflex,” which is a confusing point, since this could be misconstrued as referring to the eyes, not the ear. The vignette in which they mention this they also have multiple sclerosis as a wrong answer + mention the patient has a sibling with MS. So the Q is dumb/gotchya-style overall. The key sentence in this NBME Q is that the patient had nausea and reduced ability to eat foods past few days, which implies recent viral infection. - Waxing and waning, asymmetric tinnitus and vertigo that has a slowly progressive course over many years. - Has a familial component but no strict inheritance (i.e., the vignette can sometimes mention a relative with similar findings). Meniere - Due to defective endolymphatic drainage. - Can cause low-frequency hearing loss (i.e., patient says it is difficult to hear conversations at the dinner table with many people). This is in contrast to presbycusis, which is high-frequency hearing loss in elderly. - Aminoglycosides (i.e., gentamicin, amikacin), chemo agents like cisplatin, and loop diuretics (furosemide, ethacrynic acid) are known for ototoxicity. Drug-induced - Keep point is that this ototoxicity need not be hearing loss and can be vertigo – i.e., the patient is receiving IV Abx for endocarditis treatment and feels like the room is spinning (ototoxicity due to gentamicin). HY headache types - 11/10 lancinating, knife-like pain that occurs as episodes lasting usually 70% if symptomatic, or >80% if asymptomatic à answer = do carotid endarterectomy. Below these thresholds à answer = medical management = statin, PLUS clopidogrel OR dipyridamole + aspirin. The USMLE will actually MEHLMANMEDICAL.COM 66  MEHLMANMEDICAL.COM not be hyper-pedantic about the occlusion %s (that’s Qbank). They'll make it obvious for you which answer they want. They'll say either 90% à answer certainly = carotid endarterectomy, or they'll say 50% à answer = medical management only. There’s one NBME Q where they say a guy has a bruit but is asymptomatic, and has 10 and 30% occlusion in the left vs right carotids, respectively, and he’s already on aspirin + statin, and the answer is "maintain current regimen” à if he were symptomatic, even with low occlusion, he’d certainly need statin, PLUS clopidogrel OR dipyridamole + aspirin. - 6F + rheumatic fever + has Sydenham chorea; Q asks mechanism à answer = autoimmune disorder to the basal ganglia. - 22F + says cannot see out of left eye + examination shows no relative afferent pupillary defect; answer = conversion disorder – i.e., if he truly had impaired vision, Marcus-Gunn pupil would be present. - 38F + hoarseness of voice + various stress factors; Dx? à conversion disorder; merely be aware that hoarseness of voice is assessed for this. - Back pain worse when standing or walking for long periods of time à lumbar spinal stenosis. - Radiculopathy down an arm à cervical disc herniation. - Bilateral paresthesias in the arms in rheumatoid arthritis patient à atlantoaxial subluxation. - Bilateral paresthesias in the arms in rheumatoid arthritis patient à MRI of spine to Dx atlantoaxial subluxation. - Prior to surgery in rheumatoid arthritis patient à cervical CT or flexion/extension x-rays of cervical spine to check for atlantoaxial subluxation. - 40M + combination of LMN and UMN findings + no sensory abnormalities; Dx? à amyotrophic lateral sclerosis; make sure you memorize that there are NO sensory findings, as this is the detail most students forget. Sometimes the answer won’t be “ALS,” but will instead be “motor neuron” (i.e., they’ll ask for structural diagnosis, rather than disease name). - 1-year-old boy + hypotonia + honey consumption; Dx? à answer = ingestion of spores (honey); botulism (Clostridium botulinum). - 13M + camping trip + Bell palsy + constipation + hypotonia; Dx? à ingestion of preformed toxin from compromised canned goods. Tx = anti-toxin. MEHLMANMEDICAL.COM 67  MEHLMANMEDICAL.COM - 32M + waxing and waning tinnitus and hearing loss + difficulty hearing conversations at dinner and in groups + has family Hx of similar Sx; Dx? à Meniere disease à low-frequency hearing loss. - Mechanism for Meniere? à defective endolymphatic drainage; may attempt antihistamines and diuretics. - Viral infection + tinnitus +/- vertigo + no hearing loss; self-resolves over weeks to months; Dx? à vestibular neuritis. - Viral infection + tinnitus + hearing loss +/- vertigo self-resolves over weeks to months; Dx? à labyrinthitis. One Q on the neuro forms has presentation similar to vestibular neuritis but answer is labyrinthitis; vestibular neuritis isn’t listed as alternative answer. - 3M + pinna displaced upward and outward + fever; Dx? à mastoiditis (malignant otitis externa). - 3M + mastoiditis + next best step in Mx? à CT or MRI of the temporal bone (x-ray is wrong answer) à sounds outrageous to do a CT in a kid, but “CT of temporal bone” is answer on one of the NBMEs; in UWorld, MRI is answer + x-ray is wrong/insufficient à mastoiditis often associated with fluid collection that must be visualized + drained to prevent brain abscess. - 25M IV drug user + Tx for endocarditis + now the room is spinning; Dx? à CN VIII toxicity caused by aminoglycoside (can be hearing loss, tinnitus, or vertigo); empiric endocarditis Tx is usually gentamicin + either vancomycin or ampicillin/sulbactam. - Endocarditis patient + has stroke-like episode + fever; next best step? à IV antibiotics à septic embolus to the brain; can lead to brain abscess. - MCA stroke on dominant hemisphere (usually left-sided); HY findings? à contralateral limb + face sensory and/or motor deficits; also classically associated with Broca and Wernicke aphasias. - ACA stroke; HY findings? à contralateral lower leg sensory and/or motor dysfunction. - PCA stroke; HY findings? à contralateral hemianopsia with macular sparing. - Broca aphasia; HY findings? à non-fluent aphasia; telegraphic speech; comprehends normally but cannot communicate easily, leading to frustration; repetition impaired. - Where is Broca area? à posterior, lateral, inferior frontal lobe. - Wernicke aphasia; HY findings? à fluent aphasia; word salad; non-sensical speech + does not comprehend; repetition impaired. - Where is Wernicke area? à superior temporal gyrus (temporal lobe). MEHLMANMEDICAL.COM 68  MEHLMANMEDICAL.COM - What is conduction aphasia? à patient has only impaired repetition (arcuate fasciculus connecting Broca and Wernicke areas). - What is global aphasia? à patient has presentation of Broca and Wernicke aphasias at the same time. - What is transcortical motor aphasia? à patient sounds like he/she has Broca aphasia but repetition is intact. - What is transcortical sensory aphasia? à patient sounds like he/she has Wernicke aphasia but repetition is intact. - What is mixed transcortical aphasia? à patient sounds like he/she has Broca and Wernicke at the same time but repetition is intact. - 42M + acalculia + left-right agnosia + finger agnosia + agraphia; Dx? à Gerstmann syndrome (angular gyrus syndrome; junction of parietal and temporal lobes). - Stroke causing Horner syndrome + dysphagia + loss of pain/temp from contralateral body and ipsilateral face; Dx? à lateral medullary syndrome (PICA infarct) à “Pikachu” = PICA-chew = dysphagia with PICA infarct. - Stroke causing ipsilateral Bell palsy; Dx? à lateral pontine syndrome (AICA infarct) à FACIAL spelled backwards has AICA in it à face is affected. - Stroke causing ipsilateral tongue deviation + contralateral paralysis and loss of propioception; Dx? à medial medullary syndrome (paramedian branch of anterior spinal artery). - Lacunar infarct HY points? à caused by HTN leading to lipohyalinosis of lenticulostriate vessels à if affecting posterior limb of internal capsule, deficits are pure motor (contralateral); if thalamic, deficits are pure sensory (contralateral). - Stroke causing locked-in syndrome; Dx? à Basilar artery stroke. - Correct hyponatremia too quickly? à locked-in syndrome due to central pontine myelinolysis (osmotic demyelination). - Correct hypernatremia too quickly? à cerebral edema. - Pain in contralateral limb months after stroke resolves; Dx? à thalamic pain syndrome. - Coma or persistent vegetative state following deceleration injury (i.e., MVA or fall); Dx? à diffuse axonal injury. MEHLMANMEDICAL.COM 69  MEHLMANMEDICAL.COM - 7F + facial grimaces past 5 months + no other motor findings or abnormal sounds + mental status normal; next best step in Mx? à answer = “schedule a follow-up examination in 3 months” à Dx = provisional tic disorder à 1/5 children experience some form of tic disorder; most common ages 7- 12; usually lasts less than a year; “watch and wait” approach recommended. Provisional tic disorder used to be called transient tic disorder; the name was changed because a small % go on to develop chronic tics. - 10-month old boy + jerking movements of the limbs + EEG shows chaotic high-amplitude spikes with no recognizable pattern; Dx? à answer = West syndrome (infantile spasms) à triad of spasms + hypsarrhythmia on EEG (no recognizable pattern with high amplitude spikes) + developmental regression; international definition of the diagnosis requires two out of three; starts age 3-12 months; seen in 1-5% of Down syndrome kids; Tx = ACTH, prednisolone, or vigabatrin; ACTH is thought to act by two mechanisms: 1) stimulates steroid (cortisol) release; 2) direct (cortisol-independent) effect on melanocortin receptors. - 13M + tonic-clonic seizure + 4-month Hx of hypnagogic/hypnopompic jerking of left arm + uncle has epilepsy; Dx? à answer = juvenile myoclonic epilepsy; genetic with unclear inheritance pattern; characterized by myoclonic jerks (usually hypnagogic and/or hypnopompic) that progress to tonic- clonic seizures after several months; age of onset is usually 10-16, but can also start in adulthood; Tx is valproic acid. - 4F + few-month Hx of near-daily seizures + seizures typically occur while she’s sleeping + has started putting objects in her mouth and making less eye contact + seizures not responding to anti-epileptic meds; Dx? à answer = Lennox-Gastaut syndrome à severe childhood-onset epilepsy characterized by near-daily seizures and cognitive decline (hyperoralism is a sign of cognitive regression [babies put things in their mouths]); poor prognosis, with 5% mortality rate in childhood; 80-90% persistence of seizures into adulthood. 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