A lateral approach to the feline cerebellar fossa: case report and identification of an external landmark for the tentorium ossium

Abstract

Objectives The aim of this study was to describe the use of an external landmark that defines the attachment of the tentorium ossium for planning a craniectomy to access the cerebellar fossa. The external landmark was defined by a line where the caudal aspect of the convexity of the cranium transitions to a flat surface in the caudal aspect of the temporal fossa. We also aimed to determine if this external landmark was present and readily visualized, and to establish its relationship to the nuchal crest using three-dimensional (3D) volume-rendered CT reconstructions created from cats with normal cranial morphology. Methods First, a case is presented for the description of an approach in a cat with a meningioma located dorsolateral to the cerebellum. Second, CT studies of five cats with normal cranial morphology were selected. Regions of interest (ROIs) were drawn at the attachment of the tentorium ossium to the cranium and nuchal crest. Three-dimensional reconstructions were developed with colored ROI overlays. The external landmark defined the tentorial attachment on all 3D reconstructions. Additionally, using the postoperative CT of the clinical case described herein, ROIs of the tentorial attachment and nuchal crest along with a third ROI, the craniectomy, were drawn and overlaid on the 3D reconstruction to illustrate the position of the craniectomy in relation to the tentorium ossium attachment and nuchal crest. Results The use of the external landmark provided for a craniectomy that enabled adequate visualization for excision of a meningioma. On all 3D reconstructions, the external landmark was present and readily visualized. Conclusions and relevance Between the attachment of the tentorium ossium and nuchal crest exists an area adequately sized for a craniectomy in cats. Clinicians can use an identifiable external landmark on the lateral aspect of the cranium to plan the rostral boundary for a craniectomy to access the cerebellar fossa in cats.

Contribution of three‐dimensional printed models to neurosurgery: Description of a feline intracranial meningioma treated by rostrotentorial craniectomy

“…Resection of the rostrotentorial broad-based meningioma like in our cat was considered straightforward but intracranial lesions could be more difficult to remove because of their location, size and the involvement of adjacent tissues. 6,10,[13][14][15][16]19 The use of an intraoperative real-sized concrete model that includes bone reliefs as external landmarks would optimise the performance of a craniectomy compared to the use of two-dimensional preoperative CT or MRI images alone. 15 To overcome this limitation and because feline skull morphology may vary widely, a patient-specific full size replica is an innovative tool to improve the accuracy and safety of craniectomy.…”

“…6,10,[13][14][15][16]19 The use of an intraoperative real-sized concrete model that includes bone reliefs as external landmarks would optimise the performance of a craniectomy compared to the use of two-dimensional preoperative CT or MRI images alone. 15 To overcome this limitation and because feline skull morphology may vary widely, a patient-specific full size replica is an innovative tool to improve the accuracy and safety of craniectomy. 37 The benefits of 3D-printed models are being increasingly investigated in human neurosurgery, particularly to understand the complex anatomical features of deep-located meningiomas and to determine the best surgical route for excision.…”

“…56 Although the presence of pneumocephalus on immediate postoperative CTs, as in our case, is often described with cranioplasty procedures, it is of no consequence, but the irregular shape of our manually modelled PMMA flap may increase the chances of fracturing and migration of the implant or cosmetic concerns. 14,15,53 It has been reported that 3D-printing cranioplasty flaps, or moulding them in a 3D-printed cast, and ensuring that they are of homogenous thickness and fit perfectly on the craniofacial defect can help to avoid imperfect results. [53][54][55]57…”

“…2,6,[9][10][11][12] Various surgical approaches have been described depending on the location of the tumour. 10,[13][14][15][16] Good exposure of the lesion by craniectomy/craniotomy is a key to success as inaccurate determination of the neoplastic tissue increases the risk of iatrogenic brain damage due to excessive manipulation of the brain. 10,17 Because perioperative death has been reported as a not uncommon complication, a suitable surgical approach including craniectomy is crucial for good exposure of the tumour for debulking.…”

Formation of a meningoencephalocele after removal of a frontal lobe meningioma by transfrontal craniotomy in a cat

“…Various craniotomy procedures in cats have been published. [7][8][9] Transfrontal craniotomy for removal of neoplasia affecting the olfactory bulb and frontal lobes has been described in dogs. 10,11 Although this approach was mentioned in a large series of cats with meningiomas, a detailed procedural description is lacking.…”