Recurring hyperammonemic encephalopathy induced by bacteria usually not producing urease

Abstract

Background: Hyperammonemic encephalopathy may occur when urease-positive bacteria in the urinary tract produce ammonium which directly enters systemic circulation. Predisposing conditions such as a neurogenic bladder can increase both urinary tract infection and urine stagnation.

Case presentation: We describe the case of a 66 years old woman with a neurogenic bladder who twice developed hyperammonemic encephalopathy following urinary tract infection. During the second episode Escherichia coli and Enterococcus faecalis have been isolated in the urine. The neurologic examination showed psychomotor slowing, weak photomotor reflex, nystagmus in the lateral gaze and asterixis. The EEG showed triphasic waves which disappeared along with clinical recovery.

Conclusion: Escherichia coli and Enterococcus faecalis are commonly considered urease-negative bacteria. Although frequently involved in urinary tract infections, their role in causing hyperammonemic encephalopathy have not been previously reported. Moreover, despite only one case with a neurogenic bladder have been described so far, our is the first patient with reoccurring hyperammonemic encephalopathy secondary to urinary tract infections.

Figure 1

EEG recording showing frequent triphasic waves during hyperammonemic encephalopathy (A) and significant improvement after recovery (B). TC 0.01 s, HF 300 Hz.