Surgical treatment of rostrotentorial meningioma complicated by foraminal herniation in the cat.

OBJECTIVES: This study was performed to evaluate retrospectively the clinical signs, complications and postoperative outcomes of feline intracranial meningioma (IM) with concurrent cingulate, transtentorial and foramen magnum herniations. METHODS: The medical records and MRI scans of cats with IM and cerebral herniation were reviewed. Cases involving concurrent cingulate, transtentorial and foramen magnum herniations were included. Owners were contacted to obtain long-term follow-up information. RESULTS: Seven cats (four castrated males and three spayed females) met the inclusion criteria. Median age was 13.0 years (range 9.9-16.1 years) and median duration of clinical signs was 35 days (range 21-163 days). The clinical signs of cats with cerebral herniation included visual impairment (n = 5 [71.4%]), ataxia (n = 4 [57.1%]), impaired consciousness (n = 2 [28.6%]), head pressing (n = 2 [28.6%]), paresis (n = 1 [14.3%]), torticollis (n = 1 [14.3%]) and personality changes (n = 1 [14.3%]). Median tumour volume, cranial cavity volume and tumour volume:intracranial volume ratio before surgery were 3.37 cm3 (range 3.23-11.5 cm3), 32.6 cm3 (range 29.8-78.3 cm3) and 10.4% (range 5.3-35.3%), respectively. Median overall tumour excision rate was 90.6%. Preoperative intracranial pressure (ICP) ranged from 15 to 32 mmHg (median 29 mmHg). In all cases, the ICP dropped to 0 mmHg immediately after tumour removal. No adjuvant therapy was required after surgery. The median survival period was 612 days (range 55-1453 days). CONCLUSIONS AND RELEVANCE: The results of this study indicate that surgical treatment of rostrotentorial IM is effective and allows prolonged survival, even in cats with concurrent cingulate, transtentorial and foramen magnum herniations.

Evaluation of atlantooccipital overlapping and cerebral ventricle size in dogs with atlantoaxial instability.

This study investigated cerebral ventricle size and concurrent craniocervical junction abnormality in relation to atlantooccipital overlapping (AOO) in dogs with atlantoaxial instability (AAI). A total of 61 dogs were treated with atlantoaxial ventral fixation. Medical records of each dog, including magnetic resonance (MR) and computed tomography (CT) images, were retrospectively reviewed. CT images were assessed for the presence of AOO and the dogs were then assigned to either an AOO group or a non-AOO group accordingly. CT images were also evaluated to determine the foramen magnum (FM) index. Syringomyelia, cerebellar compression, dorsal compression, and the degree of enlargement of each cerebral ventricle were evaluated using MR images. Of the 61 dogs, 23 had AOO and 38 did not. Furthermore, the ventricle/brain height ratio, the fourth ventricle height/cerebellum length ratio, and the fourth ventricle width/cerebellum length ratio were significantly higher in the AOO group than in the non-AOO group. However, the FM index, third ventricle/brain height ratio, and incidence of syringomyelia did not differ significantly between the two groups. Dogs with concurrent AOO exhibited significantly more dilatation of the lateral and fourth ventricles.

Epidemiological and morphological characteristics of incomplete ossification of the dorsal neural arch of the atlas in dogs with atlantoaxial instability.

OBJECTIVE To retrospectively evaluate the epidemiological and morphological features and outcome of surgical treatment of incomplete ossification of the dorsal neural arch of the atlas (IODA) in dogs with atlantoaxial instability (AAI). ANIMALS 106 AAI-affected dogs that underwent ventral fixation of the atlantoaxial joint. PROCEDURES Medical records and CT images for each dog were reviewed. Dogs were allocated to 1 of 2 groups on the basis of the presence or absence of IODA or of dens abnormalities (DAs) in CT images. RESULTS Of the 106 dogs with AAI, 75 had and 31 did not have IODA; 70 had and 36 did not have DAs. Incomplete ossification was present in the cranialmost, central, or caudalmost portion of the dorsal neural arch of the atlas in 59, 39, and 28 dogs, respectively; 2 or 3 portions were affected in 29 and 11 dogs, respectively. The mean CT value (in Hounsfield units) for the midline of the dorsal neural arch of the atlas in dogs with IODA was significantly lower than that for the same site in the dogs without IODA. The mean age at surgery for dogs with central IODA was significantly higher than that of the non-IODA group. The severity of spinal cord injury before or after atlantoaxial ventral fixation did not differ between the IODA and non-IODA groups. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that concomitant DAs or IODA is common in dogs with AAI. In dogs with incomplete ossification in the central part of the dorsal neural arch of the atlas, surgical treatment of AAI generally occurs at a middle to advanced age.

Atlantooccipital overlapping and its effect on outcomes after ventral fixation in dogs with atlantoaxial instability.

We compared clinical outcomes after ventral fixation in dogs with atlantoaxial instability (AAI) on the basis of the presence or absence of atlantooccipital overlapping (AOO). Of 41 dogs diagnosed with AAI and treated ventral fixation, 12 exhibited AOO (AOO group), whereas 29 did not (non-AOO group). The AOO group had significantly higher neurological scores before (P=0.024) and 1 month after (P=0.033) surgery compared with the non-AOO group; however, no significant differences were observed between the groups 2 months after surgery. The presence of complicating AOO affected the clinical signs for dogs with AAI, but did not directly affect the outcome of surgical stabilization of AAI.