Genetics & Diagnostics in Medicine

Genetics and Associated Conditions

• MEN2B is associated with mucosal neuromas, aggressive medullary thyroid carcinoma, and pheochromocytoma
• NF1 is associated with neurofibromas, café au lait macules, axillary freckling, optic nerve glioma, iris hamartoma (Lisch nodule), long bone dysplasia, and sphenoid wing dysplasia
• Meningiomas are associated with NF2 and MEN1
• Tuberous sclerosis is associated with dental enamel pits, as well as angiofibromas
• Squamous cell carcinoma is associated with PTrH

Diagnostic Tests and Findings

• Electromyography and nerve conduction studies are part of the initial evaluation of polymyositis and dermatomyositis
• GBS typically presents with increased protein levels and normal WBC levels in CSF
• Flame hemorrhages on fundoscopy indicate retinal damage from increased blood pressure
• Abnormal T2 signal in basal ganglia without mass effect or enhancement is classic in Creutzfeldt-Jakob Disease (CJD)
• Narcolepsy is diagnosed with polysomnography and a multiple sleep latency test, treat with modafinil
• Cauda equina syndrome is diagnosed with MRI
• DAT scans (dopamine transporter) are helpful to diagnose Parkinson's disease
• Neurocysticercosis is identified on CT/MRI as calcified masses; test stool for ova and parasites
• CSF in fungal/tuberculosis meningitis shows increased lymphocytes and protein, high opening pressure, and very low glucose
• Decreased peripheral nerve conduction velocities are classic for peripheral neuropathy
• Electromyography and nerve conduction studies can show incremental increase in amplitude of evoked motor response with Lambert-Eaton syndrome
• Diagnosis of carpal tunnel syndrome can be evaluated with wrist splinting
• Carotid cavernous fistulas are diagnosed with a cerebral angiogram
• Ice water caloric testing checks brainstem function, indicated by horizontal deviation of both eyes toward affected ear
• Cavernous sinus thrombosis is diagnosed with CT/MR venography
• Lambert-Eaton myasthenic syndrome (LEMS) is dignosed with nerve conduction studies and electromyography with exercise testing.

Neurological Exam Findings and Radiculopathy

• Uncal herniation compresses the midbrain, affecting the oculomotor nerve, causing pupillary dilation, ptosis, and CN III palsy ('down and out' pupil)
• Central herniation results in decreased responsiveness, posturing, and fixed pupils
• C4 radiculopathy presents as sensory and motor dysfunction in the neck and shoulders around the acromioclavicular joint
• C5 radiculopathy presents as sensory and motor dysfunction in the lateral aspect of the shoulder and upper arm
• C6 radiculopathy presents as sensory and motor dysfunction in the lateral forearm and lateral two digits, elbow flexion, and wrist extension
• C7 radiculopathy presents as sensory and motor dysfunction in the posterior arm and forearm along with the medial three fingers
• C8 radiculopathy presents as sensory and motor dysfunction in the medial third of the hand, including the medial aspect of the fifth digit
• Ipsilateral Horner syndrome or vestibular signs indicate lateral brainstem involvement
• Numbness localized to the chin in a cancer patient can suggest mandibular metastasis compressing the mental branch of V3
• Absent ankle reflexes indicate S1 involvement
• Pcomm compression leads to CN III issues, resulting in mydriasis
• Carotid sinus hypersensitivity leads to bradycardia, syncope and hypotension
• Thenar eminence weakness or atrophy is associated with the median nerve
• Unilateral pronator drift indicates UMN lesions of the corticospinal tract, and upward drift indicates cerebellar signs

Conditions and Presentations

• Multiple sclerosis can initially present with transverse myelitis that may present with a sensory level, band-like sensation, autonomic and motor symptoms
• Diabetic thoracic radiculopathy presents with unilateral burning and electric-like pain extending from the back to the anterior abdominal midline in a dermatomal distribution
• Someone with lumbar spinal stenosis can present with neurogenic claudication made worse by standing or walking
• Hypertensive encephalopathy can manifest with headache, vomiting, agitation, AMS, seizure and coma
• Chiari malformations can present in infancy with feeding and breathing problems
• Shaken baby syndrome can present with retinal hemorrhages, apnea, and subdural or interhemispheric hemorrhages/hematoma and could be described as blood along the falx on CT head.
• Patients with idiopathic intracranial hypertension may be taking vitamin A, OCPs, or danazol
• Vertebrobasilar insufficiency can be transient (TIA) or lasting (stroke). Can cause a loss of pain and temperature sensation of the ipsilateral face and contralateral extremities
• Subdural hematomas, epidural spinal cord compression, and compressive cervical myelopathy can present with UMN signs
• Neurogenic claudication from spinal stenosis improves with forward flexion
• Ankylosing spondylitis causes morning stiffness/lower back pain that improves with exercise/stretching and enthesitis
• Meniere's disease presents with episodic vertigo, hearing loss, and tinnitus as well as unilateral sensorineural hearing loss due to increased pressure within the endolymph

Treatments and Management

• Acute dystonia due to typical antipsychotics requires anticholinergic medications like diphenhydramine or benztropine
• GBS treatment includes plasma exchange or intravenous immunoglobulin therapy
• Ethylene glycol toxicity with anion gap metabolic acidosis must be addressed with fomepizole or hemodialysis
• Treatment for narcolepsy includies modafinil
• For carbon monoxide poisoning, give 100% oxygen and then hyperbaric oxygen chamber if needed
• Treat hypertension in order to reduce your risk for vascular dementia
• Vitamin B12 deficiency (Subacute Combined Degeneration) is treatable by treating source
• Treat Bell's palsy with oral glucocorticoids (like prednisone) and antiviral therapy
• Acute cerebellar ataxia is benign and self-limited
• For Wernicke encephalopathy, thiamine should be administered BEFORE or at the same time as glucose
• Lambert-Eaton syndrome is associated with small cell lung cancer and presents with progressive proximal muscle weakness

Stroke and Circulation

• Carotid stenosis affects the anterior circulation
• Posterior circulation supplies the cerebellum, brainstem, and visual cortex

Infections: Presentations and Treatments

• Isoniazid therapy without sufficient pyridoxine can lead to pyridoxine deficiency presenting as peripheral neuropathy
• Fungal/Tuberculosis meningitis shows CSF with increased lymphocytes and protein, high opening pressure, and super low glucose
• Treat herpes simplex virus (HSV) encephalitis empirically with acyclovir, leading to increased CSF RBC count
• CSF in fungal/tuberculosis meningitis shows increased lymphocytes, protein, opening pressure, and low glucose (treat with amphotericin B.)
• HIV with multiple ring-enhancing lesions on MRI indicates Toxoplasma encephalitis; if symptoms don't improve with pyrimethamine-sulfadiazine, suspect CNS lymphoma
• Cryptococcal meningitis won't show abnormalities on CT/MRI
• For fungal infections = CSF shows low glucose, high protein, and lymphocytic/monocyte predominance

Drugs: Toxicity and Side effects

• MDMA/Molly can cause hyponatremia, hypertension, hyperthermia, agitation, bruxism, diaphoresis, and blurry vision
• SSRIs can cause dysfunction in libido, sexual arousal, and orgasm/ejaculation
• Olfactory and/or auditory aura suggest temporal lobe involvement in seizures
• Acute dystonia (neck hyperextension or repetitive upward movement of the eyes) usually occurs due to typical antipsychotics
• Changes in hormone concentrations are a common migraine trigger
• Chronic use of medications like Vitamin A, OCPs, or danazol can cause idiopathic intracranial hypertension
• Organophosphate poisoning results in too much acetylcholine and SLUDGE BBB. It is treated with atropine (antimuscarinic) + pralidoxime (regenerates ACh.)
• Amnioglycosides can cause ototoxicity and vestibulotoxicity
• A benzodiazepine such as Chloradiazepoxide can treat delirium tremens
• Bupropion (decreased dopamine and norepinephrine reuptake) is a first-line anti-depressant for those with Parkinson's
• Pyrimethamine-sulfadiazine can be used to treat toxoplasmosis
• High doses of carbidopa-levadopa can induce psychosis and schizophrenia

Miscellaneous Associations

• Alcohol-induced amnestic disorder is also called Wernicke-Korsaff’s syndrome
• Hepatolenticular degeneration is also called Wilson’s disease
• Carpal tunnel syndrome is mechanical entrapment of the median nerve
• Patients with chronic kidney disease may be at risk for vitamin B6 deficiency
• Normal memory changes that cause real distress are NOT part of normal aging
• Motor function involves the UMN (lateral corticospinal tract in the brain and spine)
• Myasthenia gravis does not cause sensory loss
• Carbidopa increases levodopa's bioavailability in the brain without inhibiting dopamine conversion
• Complex regional pain syndrome is caused by abnormal sympathetic neural response following trauma/surgery
• ALS patients die of respiratory arrest due to diaphragmatic weakness

Lobe Localization

• Pie in the sky (visual field cut) affects the Temporal lobe
• Pie on the floor (visual field cut) affects the Parietal lobe
• Frontal lobe lesions present with changes in personality or behavior
• Parietal lobe lesions lead to dominant lobe (agraphia, aphasia, agnosia, acalculia, right-left confusion) vs nondominant lobe (hemineglect on contralateral side) and sensory issues too
• Temporal lobe lesions result in receptive aphasia, dysfunctional emotional processing, hearing issues, olfactory issues, and memory issues
• Occipital lobe lesions can lead to visual loss or changes