Neurological Disorders

• These notes cover seizures, peripheral nerve disorders, multiple sclerosis, myasthenia gravis, coma, stroke, ALS, and spinal cord disorders.

Seizures

• Simple partial seizures involve numbness on one side of the body without loss of consciousness.
• Complex partial seizures involve a loss of time.
• Wellbutrin is a common drug that can induce seizures.
• Status epilepticus is a medical emergency requiring immediate intervention.
• Ativan or Versed should be administered to manage status epilepticus.

Peripheral Nerve Disorders

• Signs of peripheral nervous system (PNS) disease include lower motor neuron symptoms like atrophy and fasciculations.
• Other signs of PNS disease include hyporeflexia or areflexia and stocking glove sensory loss.
• Upper motor neuron signs such as spasticity, hyperreflexia, and an upgoing toe, indicate central nervous system (CNS) issues, not PNS.
• ALS does not typically present with sensory loss.
• In cases of suspected comprehensive lesions, plexopathy should be evaluated via imaging.
• Mononeuropathies include:
  • Median mononeuropathy at the wrist (carpal tunnel syndrome)
  • Ulnar mononeuropathy at the elbow (cubital tunnel syndrome)
  • Radial mononeuropathy ("Saturday night palsy") causing wrist and finger drop
  • Peroneal mononeuropathy (e.g., from leg crossing) leading to foot drop
• Peripheral nerves have defined sensory territories and muscle targets.
• Diabetes and impaired glucose tolerance is the number 1 cause of peripheral neuropathy.
• Always examine the feet of diabetic patients for signs of neuropathy.
• Other causes of peripheral neuropathy include B12 deficiency and hematologic or immunoglobulin disorders so SPEP should be checked.
• Complex Regional Pain Syndrome (CRPS) is often triggered by nerve trauma or injury, affecting thin sensory and autonomic nerve fibers. 90% of cases are triggered this way.

Multiple Sclerosis (MS)

• Epstein-Barr Virus (EBV) may contribute to the risk of MS.
• MS symptoms include optic neuritis, which causes loss of red color vision.
• Optic neuritis requires treatment with IV steroids rather than oral steroids.
• Lhermitte's sign (electric sensation down the back and limbs upon neck flexion) suggests the need for an MRI of the cervical spine, potentially indicating MS or spinal cord injury.
• Uthoff’s phenomenon is the temporary worsening of neurological symptoms due to increased body temperature.
• Relapsing-remitting MS (RRMS) is the most common pattern, involving attacks followed by periods of remission, potentially with some residual deficit.
• Primary-progressive MS (PRMS) is the least common pattern.
• Clinically Isolated Syndrome (CIS) is a first neurologic episode lasting over 24 hours, caused by inflammation or demyelination in the CNS.
• CIS can present with unifocal or multifocal symptoms.
• Patients with CIS and >2 T2 WM lesions on MRI are more likely to progress to Clinically Definite MS (CDMS).
• Radiological Isolated Syndrome (RIS) involves incidental MRI findings suggestive of MS in asymptomatic patients.

Myasthenia Gravis (MG)

• MG symptoms worsen as the day progresses.
• Beta blockers are contraindicated in MG because they block the neuromuscular junction.

Coma

• Coma or impaired arousal can arise from:
  • Bilateral hemisphere or diencephalon lesions
  • Primary upper brainstem lesions
  • Combined hemisphere and brainstem lesions
• Lower brainstem lesions alone do not cause coma.
• A coma exam includes assessing:
  • Level of consciousness (LOC)
  • Pupillary responses
  • Extraocular movements
  • Motor responses
  • Respiration
• Level of consciousness progresses through stages from the diencephalon to the medulla representing a progressive deterioration in function.
• *Level of Consciousness Stages
  • Diencephalon
  • Midbrain
  • Pons
  • Medulla
• Pupillary responses:
  • Parasympathetic stimulation constricts pupils.
  • Sympathetic pathways dilate pupils.
• *Pupil Stages:
  • Diencephalon: Small, reactive pupils
  • Midbrain: Midsize, nonreactive pupils (blown pupil if CNIII is directly involved)
  • Pons: Midsize, nonreactive pupils (pinpoint if direct pontine damage)
  • Medulla: Midsize, nonreactive
• A pontine pupil presents as small, constricted pupils and indicates damage to the pons.
• A blown pupil indicates direct involvement of cranial nerve III.
• Extraocular movements assess brainstem function using:
  • Vestibulo-Ocular Reflex (Cold Calorics): Eyes deviate slowly toward the irrigated side (COWS: cold-opposite, warm-same).
  • Oculocephalic Reflex (Doll’s Eyes): Eyes should move opposite to the direction of head turning; cervical injury must be ruled out first.
• *Extraocular Movement Stages:
  • Diencephalon: Brisk OCR/VOR
  • Midbrain: May be diminished, dysconjugate
  • Pons: Absent
  • Medulla: Absent
• Motor responses:
  • Above the red nuclei (midbrain): rubrospinal tract causes flexion of the arms, vestibulospinal tract causes extension of the legs.
  • Below the red nuclei: vestibular tract leads to extension of the arms and legs.
• *Motor Response Stages:
  • Diencephalon: Semi-purposeful to extension
  • Midbrain: Flexion to extensor
  • Pons: Extensor to flaccid
  • Medulla: Flaccid
• Decerebrate posturing (extensor) indicates severe brainstem damage, specifically in the midbrain or upper pons.
• Decorticate posturing (flexor) indicates damage to upper motor neurons in the cerebral hemispheres.
• Respiration patterns:
  • Diencephalon: Sighs, yawns, Cheyne-Stokes respirations
  • Midbrain: Hyperventilation (central neurogenic hyperventilation)
  • Pons: Inspiratory pauses (apneusis) or "eupnea"
  • Medulla: Ataxic breathing or apnea
• Cheyne-Stokes breathing involves alternating periods of rapid, shallow breathing and apnea.

Stroke

• Acute, severe headache is more commonly associated with hemorrhagic stroke than ischemic stroke.
• Amaurosis fugax (fleeting blindness like a shade coming down) indicates internal carotid disease/stenosis.
• 88% of strokes are ischemic.
• Ischemic stroke subtypes:
  • Large-vessel thrombotic and embolic strokes (20%) result from hypoperfusion, hypertension, and arterial emboli.
  • Small-vessel strokes (lacunar) (25%) come from plaque, diabetes, or hypertension.
  • Cardioembolic strokes (20%) originate from atrial fibrillation, valve disease, or ventricular thrombi.
  • Other types (5%) include arterial dissection, arteritis, or drug abuse.
  • The cause is unknown in 30% of ischemic strokes.
• Initiate a code stroke if a patient shows signs of stroke.
• Check blood sugar before CT scan to rule out hypoglycemia.
• CT scans might not immediately show an ischemic stroke; CTA is important to check for occlusion or aneurism.
• Ischemic stroke appears black on CT, while hemorrhagic stroke appears white.
• Except in older adults, stroke is more common in men than in women.
• Two types of hemorrhagic stroke:
  • Intracranial Hemorrhage (ICH): Bleeding into brain tissue from small, deep cortical arteries damaged by chronic hypertension.
  • Subarachnoid Hemorrhage (SAH): Bleeding into the subarachnoid space, commonly from a ruptured aneurysm or Arteriovenous Malformation (AVM).
• Putamen hemorrhage is the most common cause of ICH (50%).
• A pinched-off 4th ventricle on imaging indicates hydrocephalus; posterior fossa bleed/stroke requires ICU admission.
• Aneurysm rupture is the most common cause of non-traumatic SAH.
• The "1st and worst headache of life" suggests subarachnoid hemorrhage.
• Perform a lumbar puncture (LP) if CT is normal after a patient reports the "1st and worst headache of life".
• Arteriovenous Malformation (AVM): Tightly tangled collection of abnormal blood vessels that shunt arterial blood into the venous system without a capillary network.
• AVM is the most common cerebrovascular lesion to cause symptoms.
• Frontal lobe AVMs can cause psychiatric and behavioral changes.
• NIHSS scores range from 0-42 to grade strokes.

ALS (Amyotrophic Lateral Sclerosis)

• ALS presents with both upper and lower motor neuron findings.
• Fasciculations of the tongue is a hallmark sign and pathognomonic for ALS.
• Refer suspected ALS cases to an ALS center immediately.

Spinal Cord Disorders

• Lower motor neuron lesion: affects nerve fibers from the anterior horn of the spinal cord to muscles, causing areflexia and flaccid paralysis.
• Upper motor neuron lesion: affects neural pathways above the anterior horn causing spasticity, increased muscle tone, clasp-knife response, weakness, brisk reflexes, and Babinski or Hoffman sign.
• Dermatological landmarks and spinal cord level:
  • C2 - posterior half of the skull cap
  • C3 - area correlating to a high turtle neck shirt
  • C4 - area correlating to a low-collar shirt
  • C6 - (radial nerve) 1st digit (thumb)
  • C7 - (median nerve) 2nd and 3rd digit
  • C8 - (ulnar nerve) 4th and 5th digit, also the funny bone
  • T4 - nipples
  • T5 - Inframammary fold
  • T6/T7 - xiphoid process
  • T10 - umbilicus (important for early appendicitis pain)
  • T12 - pubic bone area
  • L1 - inguinal ligament
  • L4 - includes the knee caps
• Argyll Robertson pupils: Small, bilateral pupils that react to accommodation but not to light.
• Aides tonic pupil: Large dilated pupils non reactive to light.
• Central cord syndrome: Affects arms more than legs due to damage to large cords.
• Common cancers that metastasize to the spinal cord (most to least): breast, prostate, lung, renal.
• Epidural Abscess: S. Aureus is the most common pathogen (⅔ of cases).