Acute Stroke Diagnosis.

Stroke accounts for significant morbidity and mortality and is the fifth leading cause of death in the United States, with direct and indirect costs of more than $100 billion annually. Expedient recognition of acute neurologic deficits with appropriate history, physical examination, and glucose testing will help diagnose stroke and rule out mimicking presentations. The National Institutes of Health Stroke Scale should be used to determine stroke severity and to monitor for evolving changes in clinical presentation. Initial neuroimaging is used to differentiate between ischemic and hemorrhagic stroke or other pathologic processes. If a stroke is determined to be ischemic within four and a half hours of last known well or baseline state, determining the patient's eligibility for the administration of intravenous recombinant tissue plasminogen activator is necessary to proceed with informed decision-making for diagnostic workup and appropriate treatment options. Additional evaluation with specialized magnetic resonance imaging studies can help determine if patients can receive recombinant tissue plasminogen activator within nine hours of last known well. Subarachnoid hemorrhage should be considered in the differential diagnosis if the patient presents with rapid onset of severe headache. If radiographic imaging is negative for hemorrhage when there is high suspicion for delayed presentation of stroke, a lumbar puncture should be considered for further evaluation. Patients with cerebellar symptoms should be evaluated with a HINTS (head-impulse, nystagmus, test of skew) examination because it is more sensitive for cerebellar stroke than early magnetic resonance imaging. Additional cerebrovascular imaging should be considered in patients with large vessel occlusions presenting within 24 hours of last known well to assess benefits of endovascular interventions. Once initial interventions have been implemented, poststroke evaluations such as telemetry, echocardiography, and carotid imaging should be performed as clinically indicated to determine the etiology of the stroke.

Cerebrospinal Fluid Analysis.

Cerebrospinal fluid (CSF) analysis is a diagnostic tool for many conditions affecting the central nervous system. Urgent indications for lumbar puncture include suspected central nervous system infection or subarachnoid hemorrhage. CSF analysis is not necessarily diagnostic but can be useful in the evaluation of other neurologic conditions, such as spontaneous intracranial hypotension, idiopathic intracranial hypertension, multiple sclerosis, Guillain-Barré syndrome, and malignancy. Bacterial meningitis has a high mortality rate and characteristic effects on CSF white blood cell counts, CSF protein levels, and the CSF:serum glucose ratio. CSF culture can identify causative organisms and antibiotic sensitivities. Viral meningitis can present similarly to bacterial meningitis but usually has a low mortality rate. Adjunctive tests such as CSF lactate measurement, latex agglutination, and polymerase chain reaction testing can help differentiate between bacterial and viral causes of meningitis. Immunocompromised patients may have meningitis caused by tuberculosis, neurosyphilis, or fungal or parasitic infections. Subarachnoid hemorrhage has a high mortality rate, and rapid diagnosis is key to improve outcomes. Computed tomography of the head is nearly 100% sensitive for subarachnoid hemorrhage in the first six hours after symptom onset, but CSF analysis may be required if there is a delay in presentation or if imaging findings are equivocal. Xanthochromia and an elevated red blood cell count are characteristic CSF findings in patients with subarachnoid hemorrhage. Leptomeningeal carcinomatosis can mimic central nervous system infection. It has a poor prognosis, and large-volume CSF cytology is diagnostic.