Hyperammonemic Encephalopathy with Diffuse Cortical and Thalamic Signal Changes on Diffusion-Weighted Brain MRI

Abstract

Comorbid hyperammonemic encephalopathy (HE) and status epilepticus (SE) leading to extensive cortical diffusion restriction (CDR) on MRI have not been previously reported. We describe a patient with HE who subsequently developed provoked SE. Sequential MRIs demonstrated a progressive CDR that involved the entire bilateral supratentorial cortex, thalami, and basal ganglia, resulting in death from cerebral edema and brain herniation. Diffuse CDR is most frequently seen after hypotension or hypoxia, which our patient did not experience. Such findings have also been described in both HE and SE (Milligan et al. (2009), Chatzikonstantinou et al. (2011), U-King-Im et al. (2011), and Bindu et al. (2009), but not to the extent seen in our patient. Additionally, our patient had distinct radiologic features of both disease processes, suggesting a cumulative effect. The diagnosis of HE and SE in the setting of extensive CDR should not be missed and could lead to improved outcomes for two progressive, malignant, and treatable illnesses that can be easily overlooked. Case ReportWe present a 50-year-old female with cirrhosis secondary to chronic hepatitis C and alcohol abuse in remission who was admitted to our hospital with a three-day history of worsening abdominal pain and confusion. She was prescribed lactulose for the hepatic encephalopathy, which kept her ammonia in the normal range but had missed several doses over the preceding three days in addition to a decrease in the number of bowel movements. On initial exam the patient was normotensive and oxygenating well on room air with mild encephalopathy. A chronic ventral hernia displayed no signs of peritonitis. Labs on admission were significant for an ammonia level of 87 mol/L (18-72 mol/L), platelet level of 96 k/ L, sodium of 132 mmol/L, and international normalized ratio (INR) of 1.6. Computed tomography of her abdomen and pelvis with intravenous contrast revealed that the hernia contained dilated small bowel but no definitive obstruction.Overnight her mental status declined and by the next morning she was difficult to arouse and unable to follow commands. Vitals were within normal limits and morning labs were significant for a rise in plasma ammonia to 277 mol/L. She was electively intubated for airway protection but was not hypoxic. The following morning, on hospital day 3, she developed rhythmic clonic facial movements with eyelid fluttering, sustained tonic stiffening of the extremities, and intermittent right upper extremity jerks. The neurology service was consulted and continuous electroencephalogram (EEG) was recommended. During two hours of recording, prior to MRI imaging, there was focal status epilepticus in the left temporal region that spread to the left central and right temporal regions. 5 mg of intravenous lorazepam was administered and 1 gm levetiracetam twice daily was started, but the EEG continued to show persistent SE. She was paralyzed with vecuronium to obtain MRI of the brain with gadolinium contrast. This revealed extensive CDR involving the b...