In a previously healthy 15‑year‑old female with acute dysarthria, sudden leg weakness and sensory changes, normal laboratory studies, and a negative non‑contrast head CT, what are the differential diagnoses and should she be admitted or discharged from the emergency department?

Differential Diagnosis and Emergency Department Disposition

This 15-year-old with acute dysarthria, leg weakness, sensory changes, and a negative head CT requires hospital admission for urgent MRI and neurology consultation to rule out stroke, demyelinating disease, or other serious neurological conditions—discharge is unsafe despite normal initial workup. 1, 2

Critical Differential Diagnoses

High-Priority Diagnoses Requiring Admission

• Posterior circulation stroke or vertebrobasilar insufficiency – acute dysarthria with leg weakness is a classic presentation, and CT misses up to 25% of clinically relevant brain injuries that are visible only on MRI 1
• Demyelinating disease (multiple sclerosis, acute disseminated encephalomyelitis) – sudden onset of multifocal neurological deficits in a young female is highly suspicious, particularly with dysarthria and bilateral leg symptoms 3
• Transverse myelitis or spinal cord pathology – bilateral leg weakness with sensory changes ("legs gave out") suggests spinal cord involvement that would not appear on head CT 3
• Functional neurological disorder (conversion disorder) – remains a diagnosis of exclusion only after comprehensive neuroimaging and evaluation rule out organic pathology 4, 3

Lower-Priority but Important Considerations

• Complicated migraine with aura (hemiplegic migraine, basilar migraine) – the prior ER gave a migraine cocktail, but persistent dysarthria and weakness 24+ hours later makes this diagnosis insufficient 4
• Seizure with Todd's paralysis – post-ictal weakness can last hours but typically resolves; persistent symptoms warrant further investigation 5, 6
• Metabolic or toxic encephalopathy – though blood work was reportedly normal, confirm glucose, electrolytes, and toxicology were comprehensive 6

Why Discharge is Unsafe

• A normal non-contrast head CT does not exclude stroke, especially posterior circulation events, diffuse axonal injury, or early ischemia – diffusion-weighted MRI is the most sensitive technique during the acute phase and is essential for early detection 1
• Up to 1.5% of patients with normal initial assessments deteriorate, and 57% of these deteriorations occur within the first 24 hours – this patient already has abnormal neurological findings, placing her at even higher risk 1, 2
• Patients presenting with "nontraditional" stroke symptoms (such as isolated dysarthria, generalized weakness, or altered gait) have a 64% missed diagnosis rate in the ED – this patient's symptom constellation fits this high-risk pattern 3

Mandatory Next Steps in the Emergency Department

Immediate Actions

• Obtain urgent neurology consultation – specialized neurological assessment is essential when CT findings are incongruent with the clinical picture 1, 7
• Order brain and cervical spine MRI with diffusion-weighted imaging (DWI) – DWI is the most sensitive modality for acute neurological injury and will detect lesions missed by CT 1
• Perform comprehensive neurological examination documenting all deficits – specifically assess cranial nerves (especially VII, IX, X, XII for dysarthria), motor strength in all extremities, sensory testing, cerebellar function, and gait 2, 3
• Reassess vital signs and ensure systolic blood pressure >110 mmHg and oxygen saturation >90% – hypotension and hypoxemia worsen neurological outcomes 2

Admission Criteria Met

• Any patient with acute focal neurological deficits (dysarthria, leg weakness) and normal CT requires admission for advanced imaging and monitoring 1, 2
• Serial neurological examinations every 15 minutes for the first 2 hours, then hourly for 4-12 hours are required – this level of monitoring cannot be provided at home 2
• The combination of multiple neurological symptoms (speech, motor, sensory) in a previously healthy adolescent mandates inpatient workup – outpatient neurology follow-up is insufficient for acute presentations 7, 6

Common Pitfalls to Avoid

• Do not attribute acute neurological deficits to migraine without excluding stroke and demyelinating disease – the previous ER's migraine diagnosis was premature given persistent symptoms 4, 3
• Do not rely on normal CT to rule out serious pathology – CT frequently misses microhemorrhages, posterior circulation strokes, and early demyelinating lesions that are visible on MRI 1
• Do not discharge based on normal laboratory studies alone – blood work does not evaluate structural or inflammatory CNS pathology 6
• Do not assume functional/conversion disorder without comprehensive neuroimaging – organic disease must be definitively excluded first 3

Admission Orders and Monitoring

• Admit to neurology service or general medicine with neurology consultation 7, 6
• NPO status until swallowing evaluation completed – dysarthria may indicate bulbar dysfunction with aspiration risk 3
• Fall precautions and assistance with ambulation – documented leg weakness and "legs gave out" indicate fall risk 4
• Continuous pulse oximetry and frequent vital signs – maintain oxygen saturation >90% 2
• Document any decrease ≥2 points in GCS or development of new neurological deficits, which mandates immediate repeat imaging 2