ABSTRACT NUMBER: ESOC2026A765 L-ARGININE FOR MIGRAINOUS ENCEPHALOPATHY AND RECEPTIVE APHASIA IN A CADASIL PATIENT

Abstract Background and aims CADASIL, the most common monogenic cause of ischemic stroke and small vessel disease, can also cause episodic encephalopathy with migraine and focal deficits. However, no disease-specific therapy exists. Compared to controls, CADASIL patients have decreased ratios of l-arginine to asymmetric dimethylarginine. They also demonstrate more robust improvement of cerebral vasoreactivity from l-arginine. We aimed to examine l-arginine as a direct treatment. Methods This case report describes l-arginine treatment in a CADASIL patient with prolonged migrainous encephalopathy and receptive aphasia. Results A 47-year-old woman presented with receptive aphasia, confusion, right homonymous hemianopia, mild right-sided weakness, and severe headache. Symptoms developed across two days after a noxious smell exposure. MRI showed left parietal vascular congestion and subtle gyriform diffusion restriction, as well as T2 hyperintensities typical for CADASIL. CT angiogram, continuous EEG monitoring and CSF examination were unrevealing. Family history was consistent with CADASIL. Headache resolved with ketorolac and metoclopramide, but her profound aphasia remained unchanged over 7 days. A test dose of oral l-arginine was well-tolerated. The dose was increased to a supraphysiologic 3 grams three times daily, and aphasia & vision improved notably over the following day. Milder deficits responded well to inpatient rehabilitation over 10 days. NOTCH-3 genetic testing confirmed CADASIL. Conclusions In this CADASIL patient with migrainous encephalopathy, aphasia and left parietal vascular congestion, supraphysiologic l-arginine administration was well-tolerated and associated with significant clinical improvement. L-arginine warrants additional study as a potential treatment for migraine and encephalopathy in CADASIL patients. Conflict of interest Marlan Kay: nothing to disclose; Rachael Schutz: nothing to disclose. Figure 1 - belongs to Results