Cranial MRI in Acute Hyperammonemic Encephalopathy

Acute Hyperammonemic Encephalopathy in Adults: Imaging Findings

“…4,11,13 Our findings support the general view that these cortical changes appear to be early imaging findings and potentially reversible if aggressive treatment is instituted. 4,11 The extent of injury may be dependent on the severity and duration of the hyperammonemia and predisposing susceptibility to the metabolic insult. 2,11 Our data also suggest that the plasma ammonium levels may reflect the extent of injury.…”

“…Bilateral involvement of the insular cortex and cingulate gyrus was a strikingly common feature, seen in all our 4 patients, and these findings have also been described in several other cases, mainly in the pediatric literature. 4,11 Bindu et al 4 reported 3 cases of hyperammonemic encephalopathy in children due to various causes including infantile citrullinemia, acute hepatic encephalopathy, and proximal urea cycle disorder, with similar cortical abnormalities and involvement of the insular and cingulate cortices. Takanashi et al 11 described 3 cases of acute hyperammonemic encephalopathy arising from late-onset ornithine transcarbylamase deficiency, all with evidence of injury to the cingulate and insular cortices, and they described sparing of perirolandic and occipital cortices.…”

“…2 In the pediatric population, acute hyperammonemic encephalopathy and its imaging findings have been well described as a result of inborn errors of metabolism (eg, urea cycle disorders or organic acidemias). 3,4 In adults, this condition is more commonly encountered in very ill patients being treated in the ICU. Acute hepatic dysfunction is most frequently implicated, but other etiologies include portosystemic shunt surgery, drugs (eg, sodium valproate, asparaginase therapy, or chemotherapy), infections, hypothyroidism, multiple myeloma, and post-lung or bone marrow transplantation.…”

Magnetic Resonance Imaging Findings of Hepatic Encephalopathy in a Dog with a Portosystemic Shunt

“…In previous descriptions in the veterinary literature, HE secondary to PSS also exhibited similar lesions on MRI to those predominantly found with chronic HE [19,20]. On the other hand, the present case showed diffuse cortical lesions, which are characteristic findings of acute HE in humans, as well as features of chronic HE, such as widened sulci and a widened subarachnoid space [2,3]. It appears that acute hyperammonemia caused by PSS in present case could cause cerebral edema that leads to neurologic crisis and ultimately results in polioencephalomalacia.…”

“…In the acute form of HE, development of neurologic symptoms is precipitated by a clinical state that causes acute hyperammonemia in previously asymptomatic patients [15]. Cerebral edema following cortical laminar necrosis is suspected to be the main pathologic event associated with demonstration of diffuse cortical lesions in acute HE [2,3]. On the other hand, the chronic form of HE presents neurologic symptoms persistently or relapsing episodes continually with underlying chronic liver disease.…”