A 58-year-old woman has a history of alcohol abuse, coronary artery disease, and atrial fibrillation. Her medications include metoprolol, lisinopril, simvastatin, and warfarin. She develops urinary urgency and frequency and is treated with oxycodone and ciprofloxacin. Three days later she develops a headache, dizziness, vomiting, and has difficulty walking. On neurological examination her strength, sensation (including vibratory sensation), and reflexes are normal. She walks with an uncoordinated, unsteady gait. On testing of coordination in the upper extremities, she displays past pointing and poor rapid alternating movements with her right upper extremity. In the lower extremities, her heel-shin testing also reveals poor coordination on the right. INR is 6.5 (normal <1, therapeutic for warfarin 2.0-3.0). What is the most likely cause of her neurologic findings?
High-Yield Explanation
This patient has evidence of cerebellar dysfunction, most likely due to cerebellar hemorrhage. Many drugs (including ciprofloxacin) interact with warfarin, excessively prolong anticoagulation, and may result in spontaneous hemorrhage. Cerebellar lesions are typically associated with ataxia and dizziness. This patient's bleeding can be localized to the right cerebellar hemisphere since a focal lesion in one lobe of the cerebellum (e.g., a cerebellar tumor, hemorrhage or infarct) causes dyscoordination on the same side of the body (ipsilateral) as the lesion. Infarcts in the basal ganglia would cause extrapyramidal signs with rigidity and uncontrolled movements in addition to discoordination. Midline cerebellar lesions (most commonly alcoholic cerebellar degeneration) cause midline signs (especially gait ataxia) out of proportion to the findings in the extremities. Posterior column disease would cause sensory abnormalities (especially, loss of proprioception and vibratory sensation) rather than problems with coordination. Acute alcohol ingestion and narcotic overdose can cause dizziness and ataxia, often with nystagmus, but would not be expected to cause unilateral dysmetria.