# August 2021

- Link: https://isnr.in/august-2021/
- Published: 2021-08-01T19:18:26+05:30
- Author: ISNR

## August 2021

## **CASE HISTORY**

18 year old man was found unconscious

History of excessive somnolence, ataxia and fatigue past 5 days

No history of fever or seizures
History of head injury following road traffic accident
a year back and was on prophylactic sodium valproate therapy regularly 

Not a known case of diabetic or hypertension

**Case contributed by –**

Chaitra P Adiga, Lakshmikanthan G N, (Major)Prakash P, Sharath Kumar G G

Department of Diagnostic & Interventional radiology

Apollo hospitals, Sheshadripurum-Bangalore

![Aug Case 2021](https://isnr.in/wp-content/uploads/2021/08/Aug-Case-2021-1024x572.
jpg)

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**Figures A B, C & D: **Axial section diffusion weighted and corresponding apparent
diffusion co-efficient images showing symmetrical diffusion restriction in bilateral
cerebral cortices with sparing of perirolandic regions (arrows).  

**Figures E, F, G & H: **Axial section diffusion weighted and corresponding apparent
diffusion co-efficient images showing symmetrical diffusion restriction in bilateral
cerebral cortices predominantly in the insular cortices (curved arrows) and thalami(
arrow heads) with sparing of occipital cortices (asterisks).** **

## **Acute hyperammonemic encephalopathy**

 * Occurs due to increased production of ammonia/ reduced elimination of ammonia.

 * **Pathogenesis : **In hyperammonemic state, ammonia crosses blood brain barrier
   induces excess glutamine, an osmolyte, causing water influx leading to cerebral
   edema. Ammonia also interferes with oxidative metabolism resulting in excessive
   lactate levels.

 * Seen in the background of cirrhosis or non-cirrhotic conditions like genetic 
   disorders/ drugs/ infections. **In our case patient had high plasma concentration
   of valproic acid and drug induced hyperammonemia**.

 * **Typical MRI findings **– Bilateral symmetrical cortical signal abnormalities
   on FLAIR and DWI/ADC, predominantly in insula and cingulate gyrus with **sparing
   of occipital and perirolandic cortices**. Basal ganglia, thalami and brain stem
   are additional sites of involvement. It is also emphasized that signal changes
   distribution is independent of origin of hyperammonemia.

 * T1 hyperintense bilateral globus pallidi may be a clue to the underlying hepatic
   disease.

 * The increased intracellular osmolality caused by hyperammonemia results in a 
   reduction of choline and myoinositol peaks and a rise in the glutamine and glutamate
   peaks on proton MR spectroscopy.

 * **Differential diagnoses: **Hypoxic ischemic encephalopathy, hypoglycemic encephalopathy,
   viral encephalitis, autoimmune encephalitis, and Creutzfeldt-Jacob encephalopathy.

 * Cortical changes are potentially reversible on early treatment.

 * May result in atrophy of insula and cingular gyrus.

**References:**

1._Reis E, Coolen T, Lolli V. MRI Findings in Acute Hyperammonemic Encephalopathy:
Three Cases of Different Etiologies. Journal of the Belgian Society of Radiology.
2020;104(1):9._

2._U-King-Im JM, Yu E, Bartlett E, Soobrah R, Kucharczyk W.  Acute hyperammonemic
encephalopathy in adults: imaging findings. AJNR Am J Neuroradiol. 2011;32(2):413-
418._

3._Rosario M, McMahon K, Finelli PF. Diffusion-weighted imaging inacute hyperammonemic
encephalopathy. Neurohospitalist. 2013;3(3):125-130._