Computed tomographic features of canine intracranial and jugular foraminal masses involving the combined glossopharyngeal, vagus, and accessory nerve roots.

A chronic cough, gag, or retch is a common presenting clinical complaint in dogs. Those refractory to conservative management frequently undergo further diagnostic tests to investigate the cause, including CT examination of their head, neck, and thorax for detailed morphological assessment of their respiratory and upper gastrointestinal tract. This case series describes five patients with CT characteristics consistent with an intracranial and jugular foraminal mass of the combined glossopharyngeal (IX), vagus (X), and accessory (XI) cranial nerves and secondary features consistent with their paresis. The consistent primary CT characteristics included an intracranial, extra-axial, cerebellomedullary angle, and jugular foraminal soft tissue attenuating, strongly enhancing mass (5/5). Secondary characteristics included smooth widening of the bony jugular foramen (5/5), mild hyperostosis of the petrous temporal bone (3/5), isolated severe atrophy of the ipsilateral sternocephalic, cleidocephalic, and trapezius muscles (5/5), atrophy of the ipsilateral thyroarytenoideus and cricoarytenoideus muscles of the vocal fold (5/5), and an ipsilateral "dropped" shoulder (4/5). Positional variation of the patient in CT under general anesthesia made the "dropped" shoulder of equivocal significance. The reported clinical signs and secondary CT features reflect a unilateral paresis of the combined cranial nerves (IX, X, and XI) and are consistent with jugular foramen syndrome/Vernet's syndrome reported in humans. The authors believe this condition is likely chronically underdiagnosed without CT examination, and this case series should enable earlier CT diagnosis in future cases.

Malignant Nerve Sheath Tumor of the Hypoglossal Nerve in a Maltese Dog.

A 4 yr old male Maltese dog presented with a 1 wk history of intermittent neck pain and progressive difficulty walking. Neurologic evaluation was consistent with a left-sided brainstem lesion. On oral examination, left lingual hemiatrophy was evident suggesting hypoglossal nerve involvement. A dumbbell-shaped extra-axial mass in the left side of the caudal fossa extending extracranially through the hypoglossal canal was detected by MRI. At postmortem histologic examination, the hypoglossal nerve was diffusely infiltrated by fusiform neoplastic cells arranged in Antoni A and Antoni B patterns. This is the first description of a malignant nerve sheath tumor selectively involving the hypoglossal nerve in a dog.

A rare case of malignant vagus nerve sheath tumor presenting with multiple cranial nerve dysfunction in a dog.

A 5-year-old intact male Gascon Saintongeois dog was presented with a 6-month history of coughing, laryngeal paralysis, a deglutition disorder of gradual onset, and left-sided Horner's syndrome. The dog was admitted as an emergency for acute central vestibular signs. Magnetic resonance images identified a left extra-axial brainstem lesion extending caudally from the medulla to the vagosympathetic trunk. Histological and immunohistological examination revealed a high grade epithelioid malignant peripheral nerve sheath tumor (MPNST). This case report is the first description of a MPNST of the vagus nerve compressing the brainstem and causing multiple cranial nerve dysfunction in a dog. Key clinical message: Nerve sheath tumors have been reported in many locations arising from spinal nerve roots and cranial nerves. Although the trigeminal nerve is the most commonly affected nerve, other cranial nerves such as the vagus can be affected.

Un cas rare de tumeur maligne de la gaine du nerf vague à l'origine d'une dysfonction de plusieurs nerfs crâniens chez un chien. Un chien mâle entier de cinq ans de race Gascon Saintongeois a été présenté avec un historique de 6 mois de toux, paralysie laryngée, trouble de la déglutition d'évolution progressive et un syndrome de Claude Bernard Horner à gauche. Le chien a été admis en urgence pour des signes vestibulaires centraux. Une imagerie par résonnance magnétique a mis en évidence une lésion extra-axiale gauche localisée au niveau du tronc cérébral s'étendant caudalement de la medulla vers le tronc vagosympathique. Les examens histologique et immunohistologique ont révélé une tumeur épithéliale maligne des gaines nerveuses de haut grade (TMGN). Ce rapport de cas est la première description de TMGN du nerf vague comprimant le tronc cérébral et à l'origine d'une dysfonction de plusieurs nerfs crâniens chez un chien.Message clinique clé:Les tumeurs des gaines des nerfs ont été rapportées de plusieurs localisations prenant leur origine des racines des nerfs spinaux et des nerfs crâniens. Bien que le nerf trijumeau soit le nerf le plus fréquemment affecté, d'autres nerfs crâniens, tel que le vague, peuvent être affectés.(Traduit par Dr Serge Messier).

High dose hypofractionated frameless volumetric modulated arc radiotherapy is a feasible method for treating canine trigeminal nerve sheath tumors.

The aim of this prospective pilot study was to evaluate the feasibility and effectiveness of curative intent high dose hypofractionated frameless volumetric modulated arc radiotherapy for treatment of canine trigeminal peripheral nerve sheath tumors. Client-owned dogs with a presumptive imaging-based diagnosis of trigeminal peripheral nerve sheath tumor were recruited for the study during the period of February 2010 to December 2013. Seven dogs were enrolled and treated with high dose hypofractionated volumetric modulated arc radiotherapy delivered by a 6 MV linear accelerator equipped with a micro-multileaf beam collimator. The plans were computed using a Monte Carlo algorithm with a prescription dose of 37 Gy delivered in five fractions on alternate days. Overall survival was estimated using a Kaplan-Meier curve analysis. Magnetic resonance imaging (MRI) follow-up examinations revealed complete response in one dog, partial response in four dogs, and stable disease in two dogs. Median overall survival was 952 days with a 95% confidence interval of 543-1361 days. Volumetric modulated arc radiotherapy was demonstrated to be feasible and effective for trigeminal peripheral nerve sheath tumor treatment in this sample of dogs. The technique required few sedations and spared organs at risk. Even though larger studies are required, these preliminary results supported the use of high dose hypofractionated volumetric modulated arc radiotherapy as an alternative to other treatment modalities.

Peripheral Nerve Sheath Tumor of the Vagus Nerve in a Dog.

A peripheral nerve sheath tumor was diagnosed in a female, neutered Labrador retriever with a 6 mo history of coughing, retching, ptyalism, and left-sided Horner's syndrome. Computed tomography scan of the neck revealed a mass lesion between the carotid artery and esophagus in the mid-cervical region. Exploratory surgery was performed and an 18 cm section of thickened vagus nerve was excised. Histopathological findings and immunochemistry staining confirmed a malignant peripheral nerve sheath tumor. The tumor showed microscopic signs of malignancy, but there were no macroscopic signs of local extension or distant metastasis. This report documents a peripheral nerve sheath tumor of rare origin in dogs.

Denervation of the Tensor Veli Palatini Muscle and Effusion in the Tympanic Cavity.

An English springer spaniel was presented for right-sided atrophy of the muscles of mastication, analgesia and paralysis of the face, and vestibular dysfunction. Neurological signs were consistent with a lesion involving the pons and rostral medulla resulting in deficits in the function of the trigeminal, facial, and vestibular nerves. MRI disclosed a right-sided extraparenchymal mass consistent with a trigeminal nerve sheath neoplasm that was compressing and invading the pons and medulla. Atrophy of the muscles of mastication, innervated by the trigeminal nerve, was also observed on MRI. Additionally, effusion was present in the ipsilateral tympanic cavity. Gross and microscopic evaluation of the right tensor veli palatini muscle (TVPM) was consistent with neurogenic atrophy. Effusion in the tympanic cavity was likely the result of an inability to open the auditory tube as a consequence of paralysis of the TVPM. Without the ability to open the auditory tube, gases present within the auditory tube and tympanic cavity may be absorbed, creating a negative pressure environment that leads to fluid transudation and effusion build up. To the authors' knowledge, this is the first report to document neurogenic atrophy of the TVPM with concurrent effusion in the ipsilateral tympanic cavity.

Frameless stereotactic radiosurgery for the treatment of primary intracranial tumours in dogs.

Stereotactic radiosurgery (SRS) is a procedure that delivers a single large radiation dose to a well-defined target. Here, we describe a frameless SRS technique suitable for intracranial targets in canines. Medical records of dogs diagnosed with a primary intracranial tumour by imaging or histopathology that underwent SRS were retrospectively reviewed. Frameless SRS was used successfully to treat tumours in 51 dogs with a variety of head sizes and shapes. Tumours diagnosed included 38 meningiomas, 4 pituitary tumours, 4 trigeminal nerve tumours, 3 gliomas, 1 histiocytic sarcoma and 1 choroid plexus tumour. Median survival time was 399 days for all tumours and for dogs with meningiomas; cause-specific survival was 493 days for both cohorts. Acute grade III central nervous system toxicity (altered mentation) occurred in two dogs. Frameless SRS resulted in survival times comparable to conventional radiation therapy, but with fewer acute adverse effects and only a single anaesthetic episode required for therapy.

The association of middle ear effusion with trigeminal nerve mass lesions in dogs.

The trigeminal nerve is involved in the opening of the pharyngeal orifice of the Eustachian tube by operating the tensor veli palatini muscle. The hypothesis was investigated that middle ear effusion occurs in a more severe disease phenotype of canine trigeminal nerve mass lesions compared with dogs without middle ear effusion. Three observers reviewed canine MRIs with an MRI-diagnosis of trigeminal nerve mass lesion from three institutions. Various parameters describing the musculature innervated by the trigeminal nerve were scored and compared between dogs with and without middle ear effusion. Nineteen dogs met the inclusion criteria. Ipsilateral middle ear effusion was observed in 63 per cent (95% CI 48.4 per cent to 77.6 per cent) of the dogs. The size of the trigeminal nerve mass lesions was positively correlated with the severity of masticatory muscle mass loss (Spearman r=0.5, P=0.03). Dogs with middle ear effusion had a significantly increased generalised masticatory muscle mass loss (P=0.02) or tensor veli palatini muscle loss score (P=0.03) compared with those without. Larger trigeminal nerve mass lesions were associated with a greater degree of masticatory muscle mass loss. Masticatory muscle mass and, importantly, tensor veli palatini muscle mass was more severely affected in dogs with middle ear effusion suggesting an associated Eustachian tube dysfunction.

Magnetic resonance imaging of acquired trigeminal nerve disorders in six dogs.

The medical records and magnetic resonance (MR) images of dogs with an acquired trigeminal nerve disorder were reviewed retrospectively. Trigeminal nerve dysfunction was present in six dogs with histologic confirmation of etiology. A histopathologic diagnosis of neuritis (n=2) or nerve sheath tumor (n=4) was made. Dogs with trigeminal neuritis had diffuse enlargement of the nerve without a mass lesion. These nerves were isointense to brain parenchyma on T1-weighted (T1W) precontrast images and proton-density-weighted (PDW) images and either isointense or hyperintense on T2-weighted (T2W) images. Dogs with a nerve sheath tumor had a solitary or lobulated mass with displacement of adjacent neuropil. Nerve sheath tumors were isointense to the brain parenchyma on T1W, T2W, and PDW images. All trigeminal nerve lesions enhanced following contrast medium administration. Atrophy of the temporalis and masseter muscles, with a characteristic increase in signal intensity on T1W images, were present in all dogs.

Cranial nerve hamartoma in a dog.

An 11-year-old, male, neutered Cavalier King Charles spaniel was euthanatized because of recurrent seizures and inflammatory bowel disease. An incidental finding at necropsy was the presence of bilateral, firm, white nodules across the petrosal crest of the skull. Microscopically, the nodules were composed of normal myelinated nerve fibers within a mucinous stroma. A diagnosis of cranial nerve hamartoma was made.

Clinical and magnetic resonance imaging features of nasopharyngeal lymphoma in two cats with concurrent intracranial mass.

Lymphoma is reported to be the most common nasal and second most common intracranial neoplasm in cats. Intracranial lymphoma may occur as a primary central nervous system lymphoma or as part of multi-centric disease. Two cats were presented with histopathologically confirmed nasopharyngeal lymphoma and concurrent mass within the middle fossa of the cranial cavity, with magnetic resonance imaging suggestive of direct communication. Both cats demonstrated evidence of bilateral oculomotor nerve deficits and upper respiratory tract noise. In one cat, bilateral optic nerve deficits were also present. The magnetic resonance imaging features were similar in both cases and demonstrated a contrast-enhancing intracranial mass on the ventral aspect of the middle fossa of the cranial cavity and an adjacent mass arising from the dorsal aspect of the nasopharynx. Lymphoma should be included as an important differential diagnosis in cats presented with middle cranial fossa syndrome (in particular ophthalmoplegia) and stertor.

Nasal adenocarcinoma with diffuse metastases involving the orbit, cerebrum, and multiple cranial nerves in a horse.

A 9-year-old Trakehner gelding was examined because of right exophthalmus. Clinical findings included a lack of menace response in the right eye, reduced direct and consensual right pupillary light reflexes, ventrolateral strabismus of the right eye, mild right-sided facial asymmetry, a head tilt to the left, and increased extensor tone in the right limbs. Findings were suggestive of a multifocal lesion affecting the right forebrain; right optic, oculomotor, and facial nerves; and left vestibulocochlear nerve. Ultrasonographic examination of the right eye revealed a vascular retrobulbar mass. Computed tomographic imaging revealed a mass that filled the nasal cavity and invaded the forebrain. Necropsy revealed an undifferentiated nasal adenocarcinoma affecting the orbit with metastases to the right parotid gland, cranial cervical lymph nodes, fascial planes of the neck, and lungs. No evidence of direct involvement of the right facial and left vestibulocochlear nerves was found, suggesting the possibility of paraneoplastic peripheral neuropathy.

Paradoxical vestibular disease with trigeminal nerve-sheath tumor in a dog.

A thirteen-year old spayed female poodle was referred because of atrophy of temporal and masseter muscles on the left and head tilt and episodical circling to the right side. Additionally, decreased facial sensation, absent menace reaction, palpebral and corneal reflexes on the left side, as well as ipsilateral hemiparesis and tongue palsy were noticed. Generalised vestibular ataxia and hypermetria in the front limbs were present. Based on the clinical signs, the presumptive anatomical localization of the lesion was the cerebellopontine angle including parts of the caudal brainstem with involvement of the trigeminal, facial and hypoglossal nerves. Involvement of either flocculonodular lobe or the caudal cerebellar peduncle on the left side causing paradoxical vestibular disease was suspected. On magnetic resonance imaging a large enhancing lesion in the area of the left cerebellopontine angle involving the trigeminal nerve and compressing cerebellum and brainstem was seen. Because of the poor prognosis the dog was euthanized on the owner's request. This space occupying lesion could be identified as a trigeminal neurofibrosarcoma/schwannoma on post mortem histopathological examination.

Cervical neoplasia originating from the vagus nerve in a dog.

An eight-year-old intact male Bernese mountain dog was referred with a history of chronic vomiting, coughing and signs of respiratory distress. Other historical findings included lethargy, weight loss and choking. On presentation, clinical findings were Horner's syndrome, ipsilateral laryngeal hemiplegia, coughing, gagging, respiratory distress and vomiting. Lateral cervical radiographs showed ill-defined mineralisation in the soft tissue ventral to the third cervical vertebra, while ultrasonography of the neck revealed a well marginated heterogeneous mass with focal hyperechogenic lesions and acoustic shadowing. Results of an ultrasound-guided fine needle aspirate suggested neoplasia. At necropsy, a large tumour was detected in the ventral cervical region, originating from the right vagosympathetic trunk. In view of the infiltrating pattern, the cellular pleomorphism and the numerous mitoses on histopathological examination, the tumour was classified as a malignant peripheral nerve sheath tumour.

Probable trigeminal nerve schwannoma in a dog.

A 7-year-old male Husky dog developed atrophy of the right masseter muscle and pruritus of the right side of the face. A myogenic origin was excluded using muscular biopsy. Electrophysiologically, there was involvement of the motor and sensory fibers of the trigeminal nerve, suggesting a lesion located between the brainstem and the trigeminal ganglion. On MRI examination, a nodular mass was detected in the right caudal fossa. This mass was characterized by intense enhancement after injection of contrast medium. Because of the progressive clinical signs, electrophysiology, and MRI results, a presumptive diagnosis of a trigeminal nerve schwannoma was made. The animal's condition improved slightly with corticosteroids. The dog underwent euthanasia 3 months after initial presentation. Necropsy was not performed.

Clinical features of trigeminal nerve-sheath tumor in 10 dogs.

Nerve-sheath tumor was diagnosed in 10 dogs with clinical signs of unilateral trigeminal nerve dysfunction. Unilateral temporalis and masseter muscle atrophy were present in all cases. An enlarged foramen and distorted rostral petrous temporal bone were seen with computed tomography imaging in one case. Magnetic resonance imaging was used to identify the lesion accurately in seven cases. Surgery was performed for biopsy and lesion removal in three cases. Cases not treated had a progressive course eventually resulting in euthanasia or death. Of the cases treated surgically, one case is alive without disease progression 27 months after surgery. Survival times of the nontreated cases ranged from five to 21 months.

Central amaurosis induced by an intraocular, posttraumatic fibrosarcoma in a cat.

A 12-year-old, castrated male, domestic shorthair cat with a previous penetrating trauma to the left globe which progressed to a phthisical eye presented for acute blindness. Ophthalmic examination and electroretinography of the right eye were found to be normal. Following euthanasia, gross and microscopic examinations were completed. A left intraocular, posttraumatic fibrosarcoma with extension to the optic nerve and chiasm and induced right optic nerve fiber degeneration at the optic chiasm with necrosis leading to central amaurosis were diagnosed.