What is the appropriate urgent evaluation and management of an adult presenting with a new acute focal neurological deficit?

Urgent Evaluation and Management of Acute Focal Neurological Deficit in Adults

Perform emergent noncontrast CT head immediately for any adult presenting with a new acute focal neurological deficit to rapidly identify life-threatening conditions including intracranial hemorrhage, stroke, mass effect, or hydrocephalus. 1, 2

Immediate Assessment and Stabilization

• Assess airway, breathing, circulation, and obtain bedside finger-stick glucose immediately upon patient arrival, as hypoglycemia can mimic stroke and requires immediate correction 3, 2
• Determine time of symptom onset or last known normal to establish eligibility for time-sensitive interventions including thrombolysis (up to 9 hours with perfusion imaging) and mechanical thrombectomy (up to 24 hours) 1
• Calculate National Institutes of Health Stroke Scale (NIHSS) score to quantify deficit severity, though note that NIHSS correlates poorly with large vessel occlusion presence 1
• Obtain focused history including recent trauma, anticoagulation use, history of malignancy, fever, headache characteristics, seizure activity, and cardiovascular risk factors 1, 2

Emergent Neuroimaging Protocol

Noncontrast CT Head (First-Line)

• CT head without contrast is the optimal initial test because it can be performed rapidly, is less susceptible to motion artifact than MRI, and effectively detects acute hemorrhage, mass effect, hydrocephalus, and large territorial infarctions 1, 2
• CT identifies acute pathology in 2-45% of cases depending on patient selection, with higher yields in patients with focal deficits compared to isolated altered mental status 2
• CT effectively excludes intracranial hemorrhage before considering thrombolytic therapy, which is an absolute contraindication to treatment 1

Vascular Imaging (Concurrent with CT)

• Obtain CT angiography (CTA) of head and neck or MR angiography (MRA) immediately to detect large vessel occlusion, as mechanical thrombectomy up to 24 hours dramatically improves outcomes in LVO stroke 1
• Do not delay vascular imaging based on NIHSS score alone, as the correlation between stroke severity and LVO presence is poor; even patients with lower NIHSS scores may harbor treatable LVOs 1
• Carotid duplex ultrasound is appropriate for non-emergent evaluation of extracranial carotid stenosis in patients with transient ischemic attack or minor stroke who are candidates for carotid endarterectomy or stenting within 48 hours 1

MRI Brain (Second-Line or Complementary)

• Obtain urgent MRI brain when CT is unrevealing but clinical suspicion remains high, particularly for posterior fossa pathology, small cortical infarcts, encephalitis, or subtle subarachnoid hemorrhage 1, 4, 2
• MRI detects 70% of ischemic strokes that present with altered mental status and are missed on initial CT, making it essential when focal deficits persist despite negative CT 4, 2
• MRI with diffusion-weighted imaging (DWI) is superior to CT for detecting acute ischemia, with higher sensitivity for small infarcts and posterior circulation strokes 1, 4
• Include susceptibility-weighted imaging (SWI) sequences when evaluating for microhemorrhages, as SWI is 3-6 times more sensitive than conventional gradient-echo sequences 4

Laboratory Evaluation

• Obtain serum glucose and sodium levels in all patients, as these are the only laboratory abnormalities that consistently alter acute management of focal neurological deficits 3, 2
• Order complete blood count, coagulation studies (PT/INR, aPTT), and troponin to assess bleeding risk before thrombolysis and evaluate for cardiac sources of embolism 1
• Obtain pregnancy test in all women of childbearing age before proceeding with contrast-enhanced imaging or thrombolytic therapy 3
• Additional metabolic panels (calcium, magnesium, comprehensive metabolic panel) should be obtained only when specific clinical clues are present, such as known malignancy, renal failure, or signs of dehydration 3, 2

Differential Diagnosis Considerations

Ischemic Stroke vs. Hemorrhagic Stroke

• Ischemic stroke accounts for approximately 87% of acute strokes, typically presenting with sudden onset focal deficit that progresses smoothly over minutes to hours 1, 5
• Intracerebral hemorrhage represents 13% of strokes and classically presents with focal deficit developing while patient is active, often accompanied by headache (more common than ischemic stroke), vomiting, and elevated blood pressure 1, 5
• Clinical presentation alone is insufficient to differentiate stroke subtypes; neuroimaging is mandatory before treatment decisions 1

Seizure with Todd's Paralysis

• Todd's paralysis (transient postictal hemiparesis) can mimic acute stroke and represents a critical diagnostic pitfall, as thrombolytic therapy in this setting carries hemorrhage risk without benefit 3, 2
• Obtain emergent EEG if altered mental status persists after witnessed seizure to detect nonconvulsive status epilepticus 3
• Patients with Todd's paralysis have higher seizure recurrence risk at 1 year and warrant neurology follow-up even if symptoms resolve 3

Transient Ischemic Attack (TIA)

• TIA carries 13% stroke risk in first 90 days and up to 30% risk within 5 years, with highest risk in the first week after the event 1
• Carotid endarterectomy benefit is greatest within 2 weeks of symptom onset in patients with high-grade carotid stenosis; benefit diminishes significantly after 4 weeks in women and 12 weeks in men 1
• MRI with DWI is preferred for TIA evaluation, as noncontrast time-of-flight MRA is sufficiently sensitive to screen for culprit intracranial lesions 1

Subarachnoid Hemorrhage

• 10.3% of aneurysmal subarachnoid hemorrhage patients present with focal neurological deficit rather than isolated severe headache 6
• Mechanisms of focal deficit in SAH include intraparenchymal hematoma (45.5%), early cerebral infarction (22.7%), parenchymal compression by subarachnoid thrombus (18.2%), and Todd's paralysis from seizure (13.6%) 6
• MRI has 95% sensitivity for detecting subtle subarachnoid hemorrhage when CT is negative but clinical suspicion remains high 4

Other Mimics

• Hypoglycemia, hyponatremia, and other metabolic derangements can present with focal deficits and must be excluded immediately with point-of-care glucose and laboratory testing 3, 2
• Encephalitis should be considered when focal deficits are accompanied by fever, altered mental status, or seizures; MRI should be performed within 24-48 hours and lumbar puncture after excluding mass effect 3, 4

Lumbar Puncture Indications

• Reserve lumbar puncture for suspected meningitis or encephalitis, particularly when fever with meningeal signs, immunocompromised status, or persistent unexplained altered mental status is present 3, 4
• Perform CT head before lumbar puncture to exclude mass effect and reduce risk of herniation 3
• Lumbar puncture is not indicated for uncomplicated focal neurological deficits without signs of infection or inflammation 3

Disposition and Treatment Decisions

Acute Ischemic Stroke Management

• Follow published guidelines for emergency stroke care including consideration of intravenous thrombolysis for eligible patients within 9 hours (with perfusion imaging) and mechanical thrombectomy for large vessel occlusion up to 24 hours 1
• Perfusion imaging with CT or MRI determines eligibility for extended-window thrombolysis (4.5-9 hours) and thrombectomy (6-24 hours) by identifying salvageable penumbra 1
• In highly suspected LVO with no need for perfusion imaging to determine eligibility, proceed directly to catheter angiography for mechanical thrombectomy without delay 1

Admission Criteria

• Admit all patients with acute stroke or intracerebral hemorrhage for monitoring, risk stratification, and secondary prevention regardless of symptom severity 1
• Admit patients with TIA who have high-grade carotid stenosis for expedited carotid endarterectomy or stenting within 48 hours, as benefit diminishes rapidly after 2 weeks 1
• Admit patients with persistent abnormal neurological examination, abnormal imaging requiring inpatient management, or who have not returned to baseline 3, 2

Safe Discharge Criteria

• Patients with transient deficits who have returned to baseline, normal neurological examination, and negative or non-acute imaging findings may be discharged with urgent outpatient neurology follow-up and vascular imaging within 48 hours 1, 3
• Ensure reliable outpatient follow-up is arranged before discharge, including neurology consultation and completion of stroke workup (echocardiography, prolonged cardiac monitoring, vascular imaging if not performed) 1, 3

Critical Pitfalls to Avoid

• Do not rely solely on CT for patients with persistent focal deficits after initial negative scan, as small ischemic lesions and posterior fossa pathology are frequently missed; obtain MRI brain urgently 4, 2
• Do not delay vascular imaging in any patient with acute focal deficit, as up to 2 million neurons are lost per minute during large vessel occlusion stroke and mechanical thrombectomy benefit extends to 24 hours 1
• Do not administer thrombolytics to patients with Todd's paralysis, as the hemorrhage risk far outweighs any potential benefit; obtain history of witnessed seizure activity and consider EEG 3, 2
• Do not discharge patients with negative workup if high-risk features are present (age >60, atrial fibrillation, known vascular disease, diabetes, hypertension) without completing vascular imaging and ensuring close follow-up 1, 2
• Do not assume focal deficits in the setting of fever are solely infectious; consider both stroke and infection, as stroke risk is elevated in febrile patients and concurrent pathology is possible 1, 2