Feline meningiomas

© Sumner, JP & Simpson, DJ Surgical management of a recurrent spinal meningioma in a cat AVJ 85(7): 276-280

Non-lymphoid primary spinal tumours in cats are rare and include meningiomas, ependymomas, astrocytomas and sarcomas. Although intracranial meningiomas are the most common primary central nervous system tumour in the cat, only 4% of all feline meningiomas occur in the spinal cord. Feline spinal meningiomas are most frequently seen in cats over ten years of age, but have been reported in those a young as 3 years. There is no breed or sex predilection reported in the literature. The clinical signs associated with spinal meningiomas are those consistent with spinal cord compression and range from mild spinal pain through to complete paralysis. The onset and severity of the clinical signs appears to be dependant on the tumour's growth, its location and the degree of resultant spinal cord compression.

Removal of spinal meningiomas via dorsal laminectomy or hemilaminectomy has been reported in the literature and is the current treatment of choice in the cat and dog. Complete resection of spinal meningiomas is challenging due to the sensitivity of vital spinal cord tissue to manipulation and the difficulty in achieving wide excisional margins, increasing the likelihood of local tumour regrowth.

Spinal meningiomas are only reported sporadically in the literature, so true survival rates and recurrence rates are unknown in cats. In a case study of five cats with spinal meningiomas treated with surgical resection alone, one was alive 46 months after surgery, and the other four cats were euthanized between 1 and 20 months after surgery. Excision was believed to be complete in three of the five cats on histopathological examination. The median survival time for the four euthanized cats was estimated to be 6 months. None of these cats reportedly underwent second surgeries if local regrowth did occur. The challenges faced during surgical resection of feline spinal meningiomas may increase the likelihood of incomplete resection and hence local tumour regrowth.

Figure 1. Myelogram of a 13-year old cat with progressive hind-limb paresis and ataxia. Left lateral oblique view, showing an extradural mass effect in the region of T9	Figure 2. Intraoperative view of meningioma compressing the thoracic spinal cord at T9	Figure 3. Excised meningioma demonstrating the involvement and subsequent resection of the dorsal and ventral nerve roots.

Diagnosis

The clinical diagnosis of spinal tumours is usually based on the results of neurological examination, spinal imaging and histological examination of biopsy samples obtained at surgical exploration. Plain radiographs in cats with spinal meningiomas tend to be unremarkable. CSF samples are often normal in these cases as well. Definitive diagnosis is usually made by MRI imaging and surgical exploration.

Treatment

The current treatment of choice is surgical resection. Although the rate of occurrence of spinal meningiomas in cats havs not been explored in the veterinary literature, in humans, the recurrence of surgically resected spinal meningiomas is approximately 10-20% depending on the length of follow-up, but it has been described as low as 1.3%. This highlights the need for surgical excision to decrease the risk of recurrence.

Radiation has been used to treat feline intracranial meningiomas in isolation resulting in reduced tumour size and subsequently reduced neurological signs. Radiation in addition to surgical resection has been advocated in cats, but to date there is no data to demonstrate a clinical advantage when compared to surgery alone.