Portosystemic Shunts and Their Effect on the Nervous System

Portosystemic Shunts and Their Effect on the Nervous System

Portosystemic shunts (PSS) are common in small breed dogs and surgical correction is commonly recommended. However, there is concern about neurologic signs peri-operative for these patients. Some develop seizures, mentation changes, and other neurologic signs before shunt attenuation while others do not show signs until after shunt attenuation. Sadly, the presence of neurologic signs is a poor prognostic indicator according to many studies. One recent study looked for prognostic indicators in dogs that develop seizures post attenuation (PAS) within 7 days of surgery.  I hope you'll find the study as interesting as I did!

Study Design

This was a retrospective study including 93 dogs from 14 different institutions. 53% of dogs received prophylactic levetiracetam. There were lots of different small breeds with a median age of 34 months (range 5-124 months). 

Results

• 17.3% of the dogs had experienced at least 1 seizure prior to surgery.

• Interestingly, 78% of the dogs had exhibited neurologic abnormalities including those with seizures.

• Only 30% of dogs with PAS survived to 30 days. Yikes.

• More often those with focal seizures survived, compared to dogs with generalized seizures.

• Sadly, the most common reason for euthanasia following the shunt was the presence of uncontrolled seizures. 

Key Points

According to their multivariate analysis the only two factors associated with short term survival were 1) having a history of seizures PRIOR to shunt correction (p=.004) and 2) the development of focal PAS (p=.0003). That's it! 

So, what do we tell our clients? Well, for starters..they need to know that these pets are are risk of developing seizures even if they DON'T have surgery. But, according to this study if they do elect surgery, the development of generalized seizures is a poor prognostic indicator. 

This article was packed with other data so if you want to read the entire thing please reach out and let me know. 

Reference:
Mullins RA, Sanchez Villamil C, Selmic LE, et al. Prognostic factors for short term survival of dogs that experience post attenuation seizures after surgical correction of single congenital extrahepatic portosystemic shunts: 93 cases (2005-2018) Vet Surg.2020; 49:958-970.


That's it for now! I'm maintaining curbside service for the summer and am starting to widen my travel radius again. Please reach out if I can asist with a case. Stay safe, stay healthy!

Prevalence of Idiopathic Epilepsy in Dogs

Idiopathic Epilepsy Update!

A recent article out of the Vet Record by Dr. Rachel Hall and colleagues outlines the prevalence of idiopathic epilepsy and structural epilepsy in dogs.* I found this a very interesting read, packed with useful information so I thought I'd pass along a bit (get it?) of it to you!

Study Design and Points Worth Noting

• This is a retrospective study based out of the UK. 

• 900 cases with MRI, a neurologic examination and medical record history were included. (wow!)

• Structural epilepsy is defined as a seizure disorder secondary to an identifiable structural cause. Examples include neoplasia, meningoencephalitis, hydrocephalus, etc.

• Idiopathic epilepsy is defined as the lack of identification of a structural abnormality in a pet with 2 or more discrete seizures. 

• Small (< 10 kg), medium (10-20 kg) and large breed (>20 kg) dogs were represented in approximately the same percentage in this study.

Results of Interest (there are a lot of interesting results in this study!)

• About 50% of the dogs were between 6 months and 6 years old, and 50% were > 6 years old. 

• About half of the dogs had structural epilepsy based on abnormal MRI findings

• The other half of dogs had no significant findings on MRI and the majority were classified as having idiopathic epilepsy. (The others had toxin and metabolic disease diagnosed).

  • Prevalence of idiopathic epilepsy in dogs in the UK? 50%!

Okay, fine (you might think) how does knowing the prevalence of idiopathic epilepsy in dogs in the UK help me?

I'm glad you asked...

• Idiopathic epilepsy was the leading diagnosis for dogs between 7 months and 6 years old. Inflammatory brain disease was second.

  • Take away point? Meningoencephalitis is NOT rare! Oh, and idiopathic epilepsy is most common in the group of dogs we thought it would be most common.  

• Idiopathic epilepsy was also the leading single diagnosis (34%) for dogs over 6 years of age. HOWEVER when they combined all types of neoplasia together into one group they found 43% of dogs over 6 years of age had neoplasia making it the leading singe diagnosis in this group.

  • Take away point? Read that sentence above again! I considered making this TidBit Tuesday a one line update because it's so critical to make sure we don't forget that "old" dogs can actually have idiopathic epilepsy!

  • Also, dogs over 6 years of age had structural epilepsy more often than idiopathic epilepsy if all causes for structural epilepsy were combined. (Not surprising, I know.)

What do you do with this information?

Do a neuro exam on every patient with a seizure history!

• If the exam is NORMAL, include idiopathic epilepsy on the differential diagnoses list, regardless of age. 

• If the exam is ABNORMAL, include causes for structural epilepsy on your differential diagnoses list, regardless of age.

Thanks for reading - I hope you have a great week!

Reminder! Upcoming Webinar "The Neurologic Exam for the Busy Vet" on Wednesday May 27th 12-1pm and repeated 7-8 pm.
Check out my website at www.barnesveterinaryservices.com for details and registration.

* Hall R, et al. Estimation of the prevalence of idiopathic epilepsy and structural epilepsy in a general population of 900 dogs undergoing MRI for epileptic seizures. Vet Record 2020.