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Neurologic Signs in Cats After Portosystemic Shunt Attenuation

W. Alex Fox-Alvarez, DVM, MS, DACVS-SA, Veterinary Surgicenter Gainesville, Florida 


|September 2021

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In the literature

Strickland R, Tivers MS, Fowkes RC, Lipscomb VJ. Incidence and risk factors for neurological signs after attenuation of a single congenital portosystemic shunt in 50 cats. Vet Surg. 2021;50(2):303-311.


The etiology of abnormal neurologic signs following portosystemic shunt (PSS) attenuation surgery in cats and dogs has not been determined. Postattenuation neurologic syndrome (PANS) differs from preoperative hepatic encephalopathy and appears to affect cats more often than dogs. In one study, PANS occurred in 15 out of 25 (60%) cats undergoing surgery for PSS attenuation.1 In contrast, a study found that only 28 out of 253 (11%) dogs developed PANS after surgery2; prophylactic use of levetiracetam as a preventive against PANS was not effective.

This retrospective study of 50 cats treated for PSS aimed to identify risk factors for the development of PANS and report the incidence and patient outcomes. Thirty-one (62%) cats developed PANS; 5 of which did not survive to discharge. Neurologic signs varied in severity and ranged from mild twitching and depression to blindness and generalized seizures. 

The only risk factor identified for the development of PANS in this population was a low serum osmolality at a median 24 hours after surgery. 

No difference was noted in the occurrence of PANS in cats with intra- vs extrahepatic shunts or between cats with or without preoperative hepatic encephalopathy. Patient age and degree of surgical attenuation (partial vs complete) did not affect the incidence of PANS. Prophylactic levetiracetam was not found to decrease the risk for developing PANS in cats.

PANS was the most commonly reported cause of death in this study and is a major concern in cats with PSS. The underlying complexity of this disease may explain the inability to identify multiple risk factors in these cats. Clinicians need to understand and communicate the risks for PANS when counseling cat owners on treatment options for PSS. Although not evaluated directly in cats, surgical treatment of PSS in dogs has been documented to significantly improve quality of life and survival time compared with medical management alone.3


Key pearls to put into practice:


Signs of PANS can range from mild twitching to refractory generalized seizures.


Preoperative hepatic encephalopathy does not appear to be a risk factor for the development of PANS, and prophylactic treatment with levetiracetam did not decrease the risk for PANS in cats.


To facilitate an informed decision, owners should be counseled on the risks and potential benefits of medical and surgical management of PSS in cats.


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