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Joe Fenn, Senior Lecturer in Veterinary Neurology and Neurosurgery  

The UK’s first successful feline hypophysectomy surgery was performed at the ºÚÁÏÉç in April 2012, to treat a cat with acromegaly and diabetes mellitus. Since then, the ºÚÁÏÉç team has treated 120 cats and 25 dogs with pituitary tumours, providing treatment for pets and owners for which there have traditionally been limited options.

Over the past decade, collaboration between skilled neurosurgeons, critical care, internal medicine and anaesthesia specialists has enabled ºÚÁÏÉç Small Animal Referrals to deliver hypophysectomy treatment regularly and remain a global leader in this area.

Transsphenoidal hypophysectomy involves the removal of a tumour affecting the pituitary gland from the base of the brain through the soft palate in the mouth. Access to this area of the brain is technically difficult and the team at the ºÚÁÏÉç is helped by cutting-edge diagnostic imaging and surgical equipment, such as the Brainsight neuro-navigation system head frame.

This approach was pioneered at the ºÚÁÏÉç in 2012 by Neurology and Neurosurgery specialist, Patrick Kenny, who when reflecting on this achievement starting a decade ago, commented: "I am immensely proud of my team at the ºÚÁÏÉç and the programme we have set up. It has been extremely gratifying, not only in seeing the marked benefits to our patients and their families, but also to know we have been at the forefront of a paradigm shift in how these common and debilitating conditions are treated in our pets."

Over the six years since Patrick left the ºÚÁÏÉç, we have developed a great deal of experience with the technique and have seen a range of challenging cases. Hypophysectomy is most frequently performed at the ºÚÁÏÉç in patients suffering from acromegaly and pituitary-dependent Cushing’s syndrome, caused by hormone-producing pituitary tumours.

Acromegaly and diabetes mellitus in cats       

Although it is technically challenging, surgical hypophysectomy is now considered the optimal treatment option for feline acromegaly. Over the past 10 years of performing the procedure, the team at the ºÚÁÏÉç have placed great emphasis on using their experience to maximise patient safety and outcome, with the mortality rate falling from around 15% initially to 6% for the past 50 cats treated.

In cats with acromegaly and diabetes mellitus, hypophysectomy is associated with a 70% rate of surviving cats achieving complete diabetic remission post-operatively, with significant improvements in insulin responsiveness seen in the vast majority of the other 30% of patients. Cats typically stay at the Queen Mother Hospital for Animals for a week to 10 days post-operatively while the team stabilises their diabetes mellitus.

Hypophysectomy only involves one general anaesthetic procedure, providing an advantage over radiation therapy. Medical management of cats with acromegaly and diabetes mellitus is typically cost prohibitive and can be extremely challenging for owners to maintain effectively. The team at the ºÚÁÏÉç has also recently successfully performed hypophysectomy for the first time to treat a rare case of a dog with acromegaly, marking another landmark in the use of this procedure in pets.

Pituitary-dependent Cushing’s syndrome      

Hypophysectomy is also an excellent treatment option for pituitary-dependent Cushing’s syndrome, most often seen in dogs with pituitary tumours. Dogs typically recover very quickly post-operatively and are often discharged within five days. Resolution of the clinical signs of Cushing’s is typically dramatic and dogs demonstrate an excellent quality of life post-operatively. Although less frequently encountered, the team has also treated a handful of cats with pituitary-dependent Cushing’s syndrome.

Although other options are available for treatment of pituitary dependent Cushing’s syndrome, including life-long trilostane therapy and radiotherapy, hypophysectomy confers advantages over these options, including the removal of the growing tumour and potential for complete cessation of hormone production. Whilst radiation therapy results in a reduction of tumour size and associated neurological signs, improvements in hormone production remain very variable.