With a Stroke, Discerning ‘Mimic’ from ‘Chameleon’ Can Save a Life

Migraines and other headache disorders, which are responsible for 10% of stroke mimics, are particularly challenging because headache is one of the hallmark features of stroke. The International Headache Society’s Diagnostic Criteria for Familial Hemiplegic Migraine and Diagnostic Criteria for Syndrome of Transient Headache and Neurological Deficits with Cerebrospinal Fluid Lymphocytosis^5,6 should be consulted to narrow down symptoms specific to migraines and other headache disorders.

Brain tumors usually cause a slowly progressive decline, but 5% can present with acute, stroke-like deficits. Although these symptoms may be due to hemorrhage into the lesion, they may be secondary to extrinsic compression of vascular structures by edema, obstructive hydrocephalus, or Todd’s paresis.

Functional disorders can be triggered by panic attack or dissociative episode, and can manifest as acute weakness or sensory disturbance. Positive features of functional disease are more important than the absence of features of an organic disease. Inconsistency (eg, a patient who can walk but cannot move the leg when examined) provides an important clue.

Stroke Chameleons

“Chameleons” imitate other diseases when their tempo of onset is gradual rather than acute, or when they have symptoms that do not necessarily implicate arterial territory.

Vertigo is extremely rare in stroke. Only 3% of stroke patients present with dizziness plus additional symptoms, and only 1% with isolated dizziness.⁷ But typical stroke symptoms, such as new or worsened unilateral hearing loss, headache, or other neurological symptoms, are rarely associated with isolated vestibular neuronitis. When these are present, stroke should be suspected.

Delirium is often characterized by excessive speech production and difficulty in path finding, so these presenting symptoms often lead to a search for an underlying infective or metabolic cause. But certain strokes may also cause visual agnosia, prosopagnosia, loss of spatial orientation, speech disinhibition, problems with attention, emotional expression and empathy, poor judgment of time, and inability to comprehend non-verbal communication.

Additional “chameleons” include bilateral thalamic strokes (resembling global amnesia), limb-shaking TIA (resembling focal epilepsy), critical carotid stenosis (resembling glioma), cortical stroke (resembling peripheral nerve lesion), bilateral occipital stroke (resembling confusion/delirium), and spinal stroke (resembling cauda equine syndrome).

The authors reiterate that the diagnosis of stroke remains primarily clinical, supported by imaging. They caution that incidental findings on imaging may be misleading, so it is essential to “relate the clinical picture to the radiographic images.” And they conclude that ultimately, the risk-benefit analysis favors administration of thrombolysis, even in the event of a potential false positive.