9.2 Headaches, Seizures, Movement Disorders, & Neuromuscular Disease

Approach to Headaches & Red Flag Features

Headaches represent one of the most common neurological complaints in primary care and emergency medicine. The critical first step is distinguishing primary headache disorders (migraine, tension-type, cluster) from life-threatening secondary headache causes.

Red Flag Features: The SNOOP4 Criteria

The presence of any SNOOP4 red flag requires immediate neuroimaging (CT or MRI) and diagnostic workup:

• Systemic symptoms (fever, weight loss, night sweats, malignancy history).
• Neurological signs or focal deficits (papilledema, confusion, seizures, cranial nerve palsy).
• Onset sudden or explosive ("thunderclap" headache reaching peak intensity in $<1\text{ minute}$).
• Older age at onset (new headache presentation in patients $>50$ years of age).
• Pattern change, Positional headache (worse lying flat or standing), Papilledema, or Precipitated by Valsalva/coughing.

Primary Headache Syndromes

Exam Trap: Triptans (e.g., sumatriptan) are potent 5-HT1B/1D receptor agonists that cause coronary vasoconstriction. They are strictly contraindicated in patients with ischemic heart disease, previous MI, uncontrolled hypertension, peripheral vascular disease, or cerebrovascular disease.

Giant Cell Arteritis (Temporal Arteritis)

Giant Cell Arteritis (GCA) is a granulomatous vasculitis of medium and large arteries, predominantly affecting the extracranial branches of the carotid artery in patients $>50$ years old.

• Clinical Presentation: New localized headache, scalp tenderness (pain when combing hair), jaw claudication (pain in masseter muscles while chewing, highly specific), polymyalgia rheumatica symptoms (proximal shoulder/hip stiffness), and visual disturbances (amaurosis fugax or sudden painless monocular vision loss due to anterior ischemic optic neuropathy).
• Laboratory Findings: Markedly elevated ESR ($>50\text{ mm/h}$, often $>100\text{ mm/h}$) and elevated CRP.
• Management Rule: If GCA with visual symptoms is suspected, initiate high-dose systemic corticosteroids immediately (IV Methylprednisolone $1\text{ g/day}$ for 3 days or oral Prednisone $60\text{ mg/day}$) BEFORE obtaining a temporal artery biopsy. Do NOT delay steroid therapy for biopsy or specialist evaluation, as visual loss can become permanent within hours.

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Seizures & Status Epilepticus Management

Seizures result from abnormal, excessive, hypersynchronous neuronal activity in the brain. They are classified as focal (originating within one hemisphere) or generalized (simultaneously engaging both hemispheres).

First Unprovoked Seizure Workup

1. Serum electrolytes, blood glucose, calcium, magnesium, renal and liver function tests.
2. Toxicology screen and anti-seizure medication levels (if previously diagnosed).
3. Electroencephalogram (EEG) to assess epileptiform activity.
4. Brain MRI (preferred over CT) to rule out structural lesions (tumor, vascular malformation, stroke, cortical dysplasia).

Status Epilepticus Emergency Protocol

Status epilepticus is defined as continuous seizure activity lasting $>5\text{ minutes}$, or $\ge 2$ discrete seizures without full neurological recovery between episodes. Neuronal injury begins after 5 minutes of continuous seizure.

[Time 0-5 min]: Initial Assessment & Stabilization
  ├─ Maintain airway, suction, apply 100% O2
  ├─ Check capillary blood glucose (if < 2.8 mmol/L -> give D50W IV)
  └─ Establish IV access, continuous ECG and pulse oximetry

[Time 5-20 min]: First-Line Emergent Therapy (Benzodiazepines)
  ├─ Lorazepam 4 mg IV over 2 min (repeat once at 10 min if seizure persists)
  └─ IF NO IV ACCESS: Midazolam 10 mg IM (or Diazepam 10 mg rectally)

[Time 20-40 min]: Second-Line Urgent Control (Non-Sedating IV ASMs)
  ├─ Levetiracetam 60 mg/kg IV (max 4500 mg)
  ├─ OR Fosphenytoin 20 mg PE/kg IV
  └─ OR Sodium Valproate 40 mg/kg IV

[Time > 40 min]: Third-Line Refractory Status Epilepticus
  ├─ Endotracheal Intubation & ICU Admission
  └─ Continuous IV infusion: Propofol, Midazolam, or Pentobarbital with continuous EEG

• Canadian Driving Regulations: Following a single unprovoked seizure or status epilepticus, patients are legally restricted from driving for at least 6 to 12 months (depending on provincial highway traffic acts) until medically cleared by a neurologist.

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Movement Disorders

Parkinson's Disease (PD)

Parkinson's disease is a progressive neurodegenerative disorder caused by loss of dopaminergic neurons in the substantia nigra pars compacta, leading to dopamine deficiency in the striatum.

• Cardinal Clinical Features (TRAP):
  • Tremor: Asymmetric resting tremor ($4\text{--}6\text{ Hz}$), classic "pill-rolling" quality, decreases with voluntary movement.
  • Rigidity: Cogwheel or lead-pipe rigidity present on passive limb movement.
  • Akinesia / Bradykinesia: Slowness of movement, decreased arm swing while walking, masked facies (hypomimia), micrographia, and shuffling gait.
  • Postural Instability: Loss of postural reflexes leading to falls (typically late in disease).
• Pharmacotherapy:
  • Levodopa / Carbidopa: Most effective symptomatic therapy. Carbidopa inhibits peripheral dopa-decarboxylase, preventing peripheral conversion of levodopa to dopamine and minimizing nausea.
  • Dopamine Agonists (Pramipexole, Ropinirole): Preferred in younger patients ($<60$ years) to delay levodopa-induced motor fluctuations and dyskinesias. Watch for side effects: Impulse control disorders (pathological gambling, hypersexuality), orthostatic hypotension, and sudden sleep attacks.
  • MAO-B Inhibitors (Rasagiline, Selegiline): Mild symptomatic benefit.
  • COMT Inhibitors (Entacapone): Used as adjunct to levodopa to prevent peripheral breakdown.

Essential Tremor

Essential tremor is the most common movement disorder, often inherited in an autosomal dominant pattern.

• Key Features: Action / Postural tremor ($8\text{--}12\text{ Hz}$) affecting the hands, arms, head ("yes-yes" or "no-no" motion), or voice. Tremor worsens during purposeful movement (e.g., holding a glass of water, writing) and improves with small ingestion of alcohol.
• Treatment: First-line agents are Propranolol (non-selective beta-blocker) or Primidone (anticonvulsant).

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Neuromuscular Disorders & Emergencies

Myasthenia Gravis (MG)

Myasthenia gravis is an autoimmune disorder caused by autoantibodies directed against the post-synaptic acetylcholine receptor (AChR-Ab) or muscle-specific kinase (MuSK) at the neuromuscular junction.

• Clinical Presentation: Fatigurable muscle weakness that worsens with repetitive exertion and improves with rest. Initial symptoms frequently involve extraocular muscles: ptosis and diplopia. Fluctuating bulbar weakness (dysphagia, dysarthria, chewing fatigue) and proximal limb weakness follow.
• Diagnostic Testing:
  • Anti-AChR antibody testing (highly specific).
  • Ice Pack Test: Application of an ice pack to a ptotic eyelid for 2 minutes improves ptosis by inhibiting acetylcholinesterase enzyme activity.
  • Repetitive nerve stimulation / Single-fiber EMG (shows decremental response).
  • Chest CT: Mandatory in all newly diagnosed MG patients to screen for thymoma (thymic hyperplasia present in 65%, thymoma in 15%).
• Management:
  • Symptomatic treatment: Pyridostigmine (oral acetylcholinesterase inhibitor).
  • Chronic immunosuppression: Prednisone, Azathioprine, Mycophenolate.
  • Thymectomy: Indicated for thymoma or seropositive generalized MG.
• Myasthenic Crisis: Life-threatening emergency characterized by severe respiratory muscle weakness causing respiratory failure. Managed in ICU with Intravenous Immunoglobulin (IVIG) or Plasma Exchange (Plex) alongside mechanical ventilation. Avoid acetylcholinesterase inhibitors during crisis to prevent excessive airway secretions.
• Contraindicated Drugs: Aminoglycosides, fluoroquinolones, beta-blockers, magnesium, and neuromuscular blockers exacerbate MG.

Guillain-Barré Syndrome (GBS / AIDP)

Guillain-Barré syndrome is an acute inflammatory demyelinating polyneuropathy (AIDP) triggered by molecular mimicry following a respiratory or gastrointestinal infection (most commonly Campylobacter jejuni, CMV, or EBV).

• Clinical Features: Progressive, symmetric, ascending flaccid weakness starting in the lower extremities, accompanied by areflexia or hyporeflexia. Autonomic dysfunction (arrhythmias, labile BP, paralytic ileus) and facial nerve diplegia may develop.
• Diagnostic Confirmation:
  • Lumbar Puncture: Reveals albuminocytologic dissociation (elevated CSF protein concentration with normal CSF white blood cell count $<10\text{ cells/}\mu\text{L}$).
• Monitoring & Treatment:
  • Respiratory Monitoring: Serial measurements of Forced Vital Capacity (FVC) and Negative Inspiratory Force (NIF). An FVC $<20\text{ mL/kg}$ or NIF $< -30\text{ cm H}_2\text{O}$ indicates impending respiratory failure requiring elective intubation.
  • Disease-Modifying Therapy: IVIG ($0.4\text{ g/kg/day}$ for 5 days) or Plasma Exchange (Plex). Both are equally effective.
  • Exam Trap: Corticosteroids are ineffective and strictly contraindicated in GBS.