Clinical Analysis: 22F, Sudden Left Leg Weakness x 2 Hours, Recurrent Episodes

Key Clinical Features Summary

Differential Diagnosis (Prioritized)

1. Hemiplegic Migraine (Sporadic or Familial) - TOP DIFFERENTIAL

• Familial Hemiplegic Migraine (FHM) is an autosomal dominant channelopathy (CACNA1A, ATP1A2, SCN1A mutations) characterized by episodic, reversible, lateralized motor weakness that can range from mild hemiparesis to hemiplegia. Motor symptoms can last hours to days.
• Sporadic hemiplegic migraine has identical clinical features without a family history.
• Leg-predominant weakness is unusual but possible (most FHM involves arm/hand preferentially).
• The weakness may occur without headache in some attacks (acephalgic migraine).
• Mechanism: cortical spreading depression with associated oligemia.

"Motor weakness of hemiplegic migraine most often involves the hand and arm... the motor weakness of hemiplegic migraine can endure for several days." - Bradley and Daroff's Neurology

2. Todd's Paralysis (Post-Ictal Paresis)

• Focal seizure (particularly involving the leg area of the motor cortex/parasagittal region) can produce negative motor symptoms - paralysis without obvious convulsive activity.
• Ictal paralysis (during the seizure itself) can have abrupt onset and offset, mimicking a TIA exactly.
• Post-ictal weakness typically lasts minutes to hours then fully resolves.
• May be impossible to diagnose without EEG.

"Focal seizures can rarely produce negative motor symptoms, including paralysis... the seizure can be impossible to diagnose without EEG... seizures are usually more frequent and have a shorter duration [than TIAs]. Postictal weakness of only one limb can occur." - Bradley and Daroff's Neurology

3. TIA (ACA territory or Parasagittal)

• Although TIA is rare at age 22, it cannot be dismissed - especially in young women on OCPs (thrombophilia risk).
• Leg-only weakness without face involvement localizes to the ACA territory (medial frontal/parietal cortex - the leg area of the homunculus) or a parasagittal lesion.
• TIA is tissue-based now (not time-based) - even brief episodes can leave DWI lesions.
• Abrupt onset with no "march" of symptoms favors TIA over migraine.

"Episodic paralysis of one limb sometimes is due to a TIA. The main considerations in the differential diagnosis are migraine and seizure. Abrupt onset and absence of positive (muscle activating) motor symptoms argue in favor of TIA." - Bradley and Daroff's Neurology

4. Multiple Sclerosis

• Young female is the classic MS demographic (F:M = 3:1, peak onset 20-40 years).
• MS can cause monoplegia via a discrete parasagittal white matter plaque.
• However, onset in MS is typically subacute (hours to days, not seconds), and full resolution between episodes supports a relapsing-remitting course (RRMS).
• Paroxysmal motor symptoms in established MS (tonic spasms, paroxysmal weakness) can resemble TIA or epilepsy.

"MS can produce monoplegia secondary to a discrete white matter plaque in the cerebral hemisphere... Onset of symptoms is subacute." - Bradley and Daroff's Neurology

5. Other Differentials to Consider

Recommended Workup

Immediate

• MRI Brain with DWI/FLAIR/T2 - look for acute infarct, white matter lesions (MS plaques), structural lesion, or cortical changes
• MRA Head and Neck - vessel stenosis or AVM
• EEG - rule out ictal/inter-ictal epileptiform discharges (if Todd's suspected)
• Blood: CBC, ESR, CRP, coagulation screen (PT/aPTT), antiphospholipid antibodies (anti-cardiolipin, lupus anticoagulant, anti-β2GP1), fasting lipids, thrombophilia panel

Targeted by Differential

• Hemiplegic migraine suspected: Genetic testing (CACNA1A, ATP1A2, SCN1A), family history
• MS suspected: MRI spine (C-spine), CSF oligoclonal bands, VEPs
• TIA/stroke workup: 2D Echo (bubble study if PFO suspected), 24-48h Holter, OCP/hormonal history
• Functional: Neuropsychological assessment after organic causes excluded

Localization Summary

Bottom Line

1. Hemiplegic migraine (sporadic/familial) - especially if episodes are associated with headache, visual/sensory aura, or there is a family history
2. Todd's paralysis - if there is any evidence of subclinical seizure activity
3. TIA - must be actively excluded with urgent neuroimaging and vascular workup
4. MS - consider if MRI shows periventricular/juxtacortical white matter lesions

What to Do Next - Practical Management Plan

Context First

STEP 1 - Assess Current Status (Right Now)

• Is the weakness still present or has it resolved?
• Vitals: BP both arms, HR, SpO2, temp
• Repeat GRBS if not done recently
• Brief neuro exam: Power in left leg (grade 0-5), reflexes (hyperreflexia = UMN), plantar response (extensor = Babinski +ve)

STEP 2 - Do NOT Dismiss This as "Minor"

Investigations to Order Immediately

STEP 3 - Admit or Refer

This patient should not be sent home after just B-complex and calcium.

• If you are at a primary care / clinic setting: Refer urgently to a neurologist or shift to a stroke-capable hospital today.
• If you are at a hospital: Admit under neurology. Start monitoring.
• If symptoms are still present (ongoing weakness): This is an acute stroke until proven otherwise - activate stroke protocol immediately.

STEP 4 - Specific Treatment Depends on Diagnosis

If TIA is confirmed after MRI/workup:

• Aspirin 150-300 mg loading dose (if no bleed on CT/MRI, and no contraindication)
• Consider dual antiplatelet (aspirin + clopidogrel 75 mg) for first 21 days if high-risk TIA (per AHA 2026 guidelines - POINT/CHANCE trial data)
• Statin (atorvastatin 40-80 mg)
• Address modifiable risk factors (OCP, thrombophilia)

If hemiplegic migraine suspected (most likely):

• No aspirin needed acutely (won't help migraine)
• Acute attack: Sumatriptan is contraindicated in hemiplegic migraine - use NSAIDs + antiemetics (metoclopramide), or IV valproate
• Prophylaxis: Flunarizine, topiramate, verapamil, acetazolamide
• Refer to neurology for genetic counseling

If Todd's paralysis (post-ictal):

• Antiepileptic drug initiation (after EEG confirmation + neurology review)
• Look for underlying cortical lesion (MRI essential)

If MS suspected (after MRI shows white matter lesions):

• CSF for oligoclonal bands, VEP
• Refer to MS clinic for disease-modifying therapy

Quick Summary of Immediate Action

RIGHT NOW:
1. Check if weakness is still present
2. Take BP, do brief neuro exam
3. Arrange urgent MRI brain (DWI) today
4. Draw blood: CBC, CRP, coag screen, APS antibodies, lipids
5. Admit / refer to neurology - do NOT discharge
6. If weakness persisting → stroke protocol → CT brain STAT
7. Ask about headache, OCP use, family history of similar episodes