A 48-year-old woman with alcohol dependence is admitted with a history of seizure 6 hours after stopping alcohol. On examination, she is alert, oriented, and neurologically intact. Which investigation is most appropriate to confirm alcohol withdrawal seizure and rule out other etiologies?

Explanation

## Investigation of Choice for Alcohol Withdrawal Seizure **Key Point:** In a patient with alcohol dependence presenting with a new seizure, **CT head without contrast** is the most appropriate first-line investigation to rule out structural/intracranial pathology (subdural hematoma, intracerebral hemorrhage, stroke, tumor) before attributing the seizure to alcohol withdrawal. ### Why CT Head is the Investigation of Choice Alcoholic patients are at high risk for: - **Subdural hematoma** — due to frequent falls, coagulopathy, and cerebral atrophy (bridging veins more susceptible) - **Intracerebral hemorrhage** — hypertension and coagulopathy are common comorbidities - **Ischemic stroke** — atrial fibrillation and cardiomyopathy are prevalent - **Intracranial mass** — chronic alcohol use is associated with nutritional deficiencies and immunosuppression Per **Harrison's Principles of Internal Medicine** and standard emergency neurology guidelines, any **new-onset seizure** — even in a known alcoholic — warrants neuroimaging to exclude structural causes before a diagnosis of alcohol withdrawal seizure is confirmed. The stem explicitly asks to "confirm alcohol withdrawal seizure and **rule out other etiologies**," making CT head the most appropriate answer. ### Pathophysiology of Alcohol Withdrawal Seizure 1. Chronic alcohol use upregulates NMDA receptors and downregulates GABA-A receptors 2. Abrupt cessation → CNS hyperexcitability → seizures ("rum fits") 3. Seizures typically occur **6–48 hours** after last drink 4. Electrolyte abnormalities (hypomagnesemia, hypocalcemia) may contribute but are not the primary mechanism ### Comparison with Other Investigations | Investigation | Utility | Why NOT First-Line | |---|---|---| | **EEG** | Documents ictal/post-ictal activity | Does not rule out structural etiology; patient is post-ictal and alert | | **Serum Mg, Ca, PO₄** | Identifies correctable metabolic contributors | Important adjunct but does NOT rule out structural causes; electrolyte abnormalities do not confirm withdrawal seizure | | **Lumbar puncture** | Excludes meningitis/encephalitis | Indicated only if fever, meningeal signs present; not indicated here | **Clinical Pearl (Harrison's):** In alcoholic patients with new seizure, CT head is mandatory to exclude subdural hematoma — a diagnosis that can be missed if the seizure is prematurely attributed to withdrawal. Neurological intactness at the time of examination does NOT exclude an evolving subdural hematoma. **High-Yield:** The question stem asks to "rule out other etiologies" — this is the defining task of CT head, not serum electrolytes. Electrolytes guide management after structural causes are excluded. **Mnemonic — Alcohol Withdrawal Seizure Workup:** **CELS** = CT head first → Electrolytes → Liver function → Seizure prophylaxis (benzodiazepines).