A 10-year-old castrated male domestic shorthair cat was referred for surgical removal of a presumed left frontal lobe meningioma detected during CT by the referring veterinary clinic. Reported clinical signs included generalised tonic–clonic seizures, altered mentation, pupillary changes, and shaking and scratching of the head. Haematology and blood chemistry were within normal limits. The cat was initially treated with prednisolone (0.4 mg/kg PO q24h [Prednisolon; Streuli]) 5 days before referral. At presentation, neither physical nor neurological examination revealed abnormal findings. The CT study performed by the referring veterinary clinic showed a round, solitary, well-delineated and isodense, space-occupying lesion with marked homogeneous contrast enhancement in the left frontal lobe (). Based on the imaging characteristics a meningioma was suspected. Thoracic radiographs and abdominal ultrasound showed no abnormalities. Medetomidine (4 µg/kg IM [Dormitor; Provet AG]), methadone (0.2 mg/kg IM [Methadon; Streuli]) and propofol (2.8 mg/kg IV [Propofol MCT; Fresenius Kabi AG]) were used for sedation and induction of anaesthesia. After intubation, oxygen with sevoflurane (Sevoflurane; Baxter AG) and fentanyl (5 µg/kg/h IV [Fentanyl Janssen; Janssen-Cilag]) was used to maintain anaesthesia. The cat received cefazoline (22 mg/kg IV [Kefzol; Teva Pharma]), esomeprazole (1 mg/kg IV [Esomep; AstraZeneca AG]) and mannitol (0.5 g/kg IV [Mannitol Bichsel; Grosse Apotheke Dr G Bichsel AG]) before surgery. The surgical procedure was broadly based upon the description of a modified transfrontal craniotomy in dogs. The fur was clipped from the lateral canthus of the eyes to the occipital protuberance and laterally to the zygomatic arches. The skin was prepared aseptically and the cat was placed in sternal recumbency with the head elevated ~30°. Anatomical landmarks in cats differ from those in dogs. In dogs the bregma landmark, a point on the midline where the left and right frontoparietal sutures meet, demarcates the caudal extent of the frontal sinus. In cats this point can hardly be palpated. Instead, a transverse line from the rostral border of the zygomatic process of the frontal bone at its insertion was drawn to the other side to identify the caudal extent of the frontal sinus (). The skin was incised at the midline extending 4 cm caudally from the caudal end of the nasal bones. Subcutis, fascia and periosteum were bluntly retracted with a periosteal elevator. Bilateral transfrontal craniotomy was started by drilling a 1.1 mm hole at the mid-point in the aforementioned imaginary line (Battery reamer/drill; DePuy Synthes). The cut was continued rostrolaterally at an angle of 30° and a length of 0.5 cm and then back in a rostromedial direction to the junction of the nasal bones. The same procedure was performed on the opposite side. The cut created a diamond-shaped bone plate, which was removed by using a periosteal elevator. Removal of the relatively thin bone was complicated by firm attachments to underlying bony septi and ethmoturbinates within the frontal sinus. The bone plate was stored in a saline container and saved for replacement at the end of the procedure. After careful removal of the ethmoturbinates, exposing the internal table of the sinus, the cranial cavity was opened with a 2.0 mm bone burr (∏-drive; Stryker). Fine Kerrison rongeurs were used to expose the frontal lobes and the overlying mass. After incision of the dura, the mass was gently mobilised by grabbing its surface with atraumatic forceps and removing attachment with surrounding tissue using iridectomy scissors. The mass was removed en bloc and was submitted for histological examination. Haemorrhage from the excisional area was minimal and was controlled with bipolar cauterisation and gauze sponges. The operation site was intensively flushed with physiological saline. The dura was left open and no grafts were placed over the defect. Neither cerebrospinal fluid (CSF) leakage nor haemorrhage were observed at the end of the procedure. The bone plate was replaced after drilling three holes with a 2 mm burr close to the lateral and caudal borders and corresponding levels of the frontal bone. A monofilament of polydioxanone (PDS 3-0; Ethicon) was used to attach the bone fragment. The fascia and the subcutis were separately sutured in a continuous pattern. The skin was closed with interrupted sutures (Supramid 4-0 [B Braun Medical AG]). Postoperatively, the cat was sedated for the first 12 h with dexmedetomidine (0.5 µg/kg/h IV [Dexdomitor; Provet AG]). Further cefazoline (22 mg/kg PO q12h), gabapentin (10 mg/kg PO q8h [Gabapentin Mepha; Mepha Pharma AG]), buprenorphine (20 µg/kg IV q6h [Temgesic; Indivior AG]), prednisolone (0.4 mg/kg PO q24h) and phenobarbital (2 mg/kg PO q12h [Aphenylb-arbit; Streuli]) were administered. One day after surgery the cat started eating and no abnormalities were found on physical examination. Neurological examination revealed an absent menace reaction on the right side and mydriatic pupils bilaterally responsive to light normally. The cat was mildly hemiparetic with decreased postural reactions on the right side. After 3 days, the cat was discharged with cefazoline and a tapering dosage of prednisolone for 7 days and phenobarbital for the next 4 weeks. Histological diagnosis was of a fibroblastic meningioma (World Health Organization grade 1). Six months after surgery, follow-up examination showed persisting mild proprioceptive deficits and a mild hemiparesis on the right side. No further neurological deficit was found. The owner did not report any abnormalities. The cat still received phenobarbital (2mg/kg PO q12h). A scheduled MRI (Philips Ingenia 3.0T; Philips AG) was performed to exclude incomplete tumour removal or regrowth with the following sequences: T2-weighted (T2W) sagittal, transverse and dorsal; T2W gradient echo transverse; transverse fluid-attenuated inversion recovery (FLAIR); T1-weighted three-dimensional ultrafast gradient echo pre- and post-contrast agent injection; and transverse susceptibility-weighted images. At the craniotomy site, a round, well-demarcated heterogeneous lesion protruded through the missing internal lamina of the left frontal bone into the left frontal sinus (1.6 × 1.0 × 0.9 cm). The lesion was continuous with the brain parenchyma of the left cerebral hemisphere. Within the lesion fluid was present, which was isointense compared with CSF in T2, hypointense in FLAIR and hypointense in T1. No contrast enhancement of the lesion itself was noted. Mild contrast uptake was visible within the rostral margin of the bony frontal sinus. Also, a small portion of cerebral cortex bulged into the fluid-filled lesion and a thin, septum-like structure isointense to white matter extended throughout the lesion. Based upon the MRI findings, a nasofrontal meningoencephalocele herniating into the left frontal sinus was assumed (). Because of the mild, non-progressive neurological deficits surgical treatment was not considered, although another underlying cause of the neurological deficits could not be excluded. Further management included anticonvulsive treatment with phenobarbital (2 mg/kg PO q12h) only. Thirty-one months after removal of the meningioma the cat was still alive without further neurological progression. The referring veterinarian informed us about the development of hyperthyroidism and hypertrophic cardiomyopathy. The owner reported weight loss and that the cat had become weaker. Otherwise the cat was doing well.