Diagnostic Values of Clinical and Magnetic Resonance Findings in Presumptive Trigeminal Neuropathy: 49 Dogs.

The goal of this retrospective, cross-sectional study was to describe the different etiologies of trigeminal neuropathy based on clinical and MRI findings and to evaluate the significance of associated concomitant disorders. MRI studies of 49 dogs with trigeminal neuropathy were blindly reviewed and were classified into the following three groups: neoplasia, neuritis, or idiopathic trigeminal neuropathy (ITN). Thirty-one percent were suspected to have neoplasia (all unilateral), 16% to have neuritis (1 bilateral and 7 unilateral), and 53% to have ITN (4 unilateral and 22 bilateral). Dogs with clinical bilateral trigeminal dysfunction were most likely to have a diagnosis of ITN (predicted probability 95.7%). Unilateral clinical signs were significantly associated with neoplasia or neuritis compared with ITN (P < .001 and P = .002, respectively). Even with marked brainstem neoplastic involvement, central neurological deficits may be absent. Sensory impairment was significantly associated with either neoplasia or neuritis compared with ITN (P = .007 and P = .03, respectively). Ipsilateral noninfectious middle ear effusion was only seen in dogs with neoplasia (33%). Horner's syndrome was present in 12% of all dogs (2 dogs in each group). Dogs with neoplasia were significantly older than dogs with neuritis (P = .02) and ITN (P = .002). JAAHA-MS-6997.

A Salivation Abnormality with Trigeminal Nerve Dysfunction in Dogs.

Trigeminal nerve pathology can lead to sensory and motor dysfunction to structures of the head that are easily recognized. The trigeminal nerve is a conduit for the distribution of postganglionic parasympathetic innervation to structures of the head. Parasympathetic innervation to the salivary glands is provided by preganglionic parasympathetic neurons of the facial and glossopharyngeal nerves. Postganglionic axons course with branches of the mandibular branch of the trigeminal nerve to reach the salivary glands. Denervation of the salivary glands impacts glandular function, leading to a reduction in the volume and composition of the saliva produced. Saliva plays an important role in oral health. Poor oral health has widespread systemic implications. This article describes a group of dogs with unilateral or bilateral dysfunction of the trigeminal nerve and/or its branches. In all dogs, an accumulation of thick, foamy saliva was observed accumulating in the dorsal aspect of the caudal oral cavity on the ipsilateral side to the affected nerve. In dogs with magnetic resonance imaging (MRI), there was a reduction in size based on the largest cross-sectional area measurement and an increase in mean signal intensity of the salivary glands ipsilateral to the affected nerves compared to the glands on the normal side. The authors hypothesize that the abnormal saliva and MRI changes observed were consequent to parasympathetic denervation of the salivary glands. The recognition of this clinical observation is the first step in understanding the impact that denervation has on salivation and ultimately on overall oral and systemic health in dogs.

Clinical findings and outcome of dogs with unilateral masticatory muscle atrophy.

BACKGROUND: Little is known about the spectrum of underlying disorders in dogs with unilateral masticatory muscle (MM) atrophy. OBJECTIVES: To evaluate the clinical presentation, magnetic resonance imaging (MRI) findings, and outcome of dogs with unilateral MM atrophy. ANIMALS: Sixty-three client-owned dogs. METHODS: The medical database was retrospectively reviewed for dogs that underwent MRI for evaluation of unilateral MM atrophy. Imaging studies were reviewed and follow-up information was obtained from telephone interviews. RESULTS: Presumptive trigeminal nerve sheath tumor (pTNST) was diagnosed in 30 dogs (47.6%); survival time varied from 1 day to 21 months (median, 5 months). Other extra-axial mass lesions were observed in 13 dogs (20.6%); survival time varied from 6 days to 25 months (median, 2.5 months). In 18 dogs (28.6%), no abnormalities were observed on MRI; neurological signs only progressed in 1 dog. Diagnosis had a significant influence on the type of neurological abnormalities, with additional neurological deficits observed in most dogs with pTNST and in all dogs with other extra-axial mass lesions. Diagnosis had a significant effect on euthanasia at the time of diagnosis and likelihood of neurological deterioration. Dogs with mass lesions were more likely to be euthanized or experience neurological deterioration, whereas these outcomes occurred less often in dogs in which no causative lesion could be identified. CONCLUSIONS AND CLINICAL IMPORTANCE: Trigeminal nerve sheath tumors should not be considered the only cause of unilateral MM atrophy. Our results illustrate the importance of performing a neurological examination and MRI when evaluating dogs with unilateral MM atrophy.

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.

Clinical and imaging findings, treatments, and outcomes in 27 dogs with imaging diagnosed trigeminal nerve sheath tumors: A multi-center study.

The clinical behavior of canine trigeminal nerve sheath tumors and benefits of previously reported treatments are incompletely defined. Aims of this retrospective, multicenter, observational study were to describe clinical signs, tumor localization characteristics, treatments, and clinical outcomes in a group of dogs with this neoplasm. Databases at four hospitals were reviewed for dogs with a trigeminal nerve sheath tumor diagnosis, magnetic resonance imaging (MRI) studies, and presentation between 2004 and 2014. A single observer recorded medical record findings and two observers recorded MRI characteristics by consensus. A total of 27 dogs met inclusion criteria (15 treated with stereotactic radiation therapy and 12 unirradiated). Two unirradiated dogs were excluded from outcome analyses. The most common presenting signs were masticatory muscle atrophy (26 dogs), neurologic signs referable to intracranial disease (13), and ocular disease (12). Based on MRI findings, all dogs had disease extending centrally at the level of the brainstem. The most commonly affected trigeminal nerve branches were the mandibular (26 dogs), maxillary (22), and ophthalmic (10). Of 15 dogs treated with stereotactic radiation therapy, one had improved muscle atrophy, and six had poor ocular health after treatment. Neurologic signs improved in 4/5 dogs with intracranial signs. Overall median survival time for the 10 unirradiated dogs with available follow-up was 12 days and 441 days for the 15 stereotactic radiation therapy dogs. Mean survival times between these groups were not significantly different (mean 95% CI for unirradiated dogs was 44-424 days and mean 95% CI for stereotactic radiation therapy dogs was 260-518 days).

Treatment of MRI-Diagnosed Trigeminal Peripheral Nerve Sheath Tumors by Stereotactic Radiotherapy in Dogs.

BACKGROUND: Stereotactic radiotherapy (SRT) is an emerging technique for treating tumors in animals. OBJECTIVES: To assess the outcome of dogs with suspected intracranial trigeminal nerve peripheral nerve sheath tumors (PNST) treated with SRT. ANIMALS: Eight dogs with presumptive PNST. METHODS: This was a retrospective study of dogs identified by searching UC Davis Veterinary Medical Teaching Hospital medical records for dogs treated with SRT for a presumed PNST. Presumptive diagnosis was based on magnetic resonance imaging. SRT was delivered in 3 dose fractions of 8 Gray (Gy) on consecutive days or every other day to a total dose of 24 Gy. RESULTS: Median disease-specific survival was 745 days (range: 99-1375 days, n = 6). No signs of acute adverse effects of radiation treatment were recorded. Late radiation effects versus tumor progression could not be confirmed histopathologically because of few animals undergoing necropsy. CONCLUSIONS AND CLINICAL IMPORTANCE: This study provides preliminary evidence that dogs with PNST benefit from SRT in terms of long-term survival. The treatment appears to be well tolerated and requires fewer anesthetic events for animals compared to full-course radiation.

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.

Prevalence of effusion in the tympanic cavity in dogs with dysfunction of the trigeminal nerve: 18 cases (2004-2013).

BACKGROUND: Animals with disorders involving the trigeminal nerve or its nuclei in the brainstem can have effusion in the tympanic cavity ipsilateral to the side of the neurological deficits. The tensor veli palatini muscle (TVP), innervated by the mandibular branch of the trigeminal nerve, opens the pharyngeal orifice of the auditory tube. With denervation of the TVP, dysfunction of the auditory tube may occur, which could lead to effusion. HYPOTHESIS/OBJECTIVES: To determine the prevalence of effusion in the tympanic cavity in dogs with disorders involving the trigeminal nerve. ANIMALS: Eighteen client-owned dogs were evaluated retrospectively. METHODS: Retrospective study. RESULTS: Diagnostic imaging databases were searched for dogs having undergone magnetic resonance imaging (MRI) evaluation for signs referable to dysfunction of the trigeminal nerve. Signalment and neurological examination findings were recorded. The MRI study was evaluated for the presence or absence of effusion. MRI characteristics of the affected trigeminal nerve and the muscles of mastication were recorded. Based on the location of the trigeminal nerve lesion, dogs were divided into three categories: brainstem, trigeminal canal, or extracranial. Eighteen dogs met the inclusion criteria. Six of 18 dogs (33%) had effusion in the tympanic cavity ipsilateral to the affected trigeminal nerve. CONCLUSION AND CLINICAL IMPORTANCE: A substantial proportion of dogs with a lesion affecting the trigeminal nerve had effusion in the tympanic cavity. This finding likely represents denervation of the TVP muscle, which may have led to dysfunction of the auditory tube.

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.

Trigeminal and polyradiculoneuritis in a dog presenting with masticatory muscle atrophy and Horner's syndrome.

A 9-year-old, spayed female, Airedale Terrier was euthanatized and necropsied after a progressive clinical course that included Horner's syndrome of the left eye and unilateral atrophy of the masticatory muscles. Although gross lesions were limited, a polyradiculoneuritis and ganglionitis that was most severe in the trigeminal nerves and ganglia were confirmed histologically. The inflammatory infiltrate consisted predominantly of macrophages and B and T lymphocytes that were phenotypically confirmed by immunostaining. Horner's syndrome was the result of damage to postganglionic sympathetic fibers that were incorporated in segments of the inflamed trigeminal nerve and its ophthalmic branch. Histologically, the character and distribution of the inflammation was similar to previously described syndromes of suspected immune-mediated etiology in humans and animals.

Trigeminal neuropathy in dogs: a retrospective study of 29 cases (1991-2000).

The medical records of 29 dogs unable to close their mouths due to flaccid paralysis or paresis of the muscles innervated by the mandibular branch of the trigeminal nerve, were reviewed. Idiopathic trigeminal neuropathy was diagnosed in 26 dogs based on complete resolution of clinical signs and lack of any long-term neurological disease. Of these dogs, golden retrievers were overrepresented. No age, sex, or seasonal predispositions were identified. Trigeminal sensory innervation deficits were observed in 35% (9/26), facial nerve deficits were observed in 8% (2/26), and Horner's syndrome was observed in 8% (2/26) of dogs. Electromyographic examination of the muscles of mastication revealed abnormalities in seven of nine dogs. Results of cerebrospinal fluid analysis were abnormal in seven of eight dogs. Corticosteroid therapy did not affect the clinical course of the disease. Mean time to recovery was 22 days. Lymphosarcoma, Neospora caninum infection, and severe polyneuritis of unknown origin were diagnosed in three of 29 dogs at necropsy.

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.

Acute bilateral trigeminal neuropathy associated with nervous system lymphosarcoma in a dog.

A nine-year-old dog presented with clinical signs consistent with bilateral trigeminal neuropathy. Multicentric lymphoma was diagnosed, and neoplastic lymphocytes were identified in the cerebrospinal fluid. Electromyography revealed spontaneous activity in temporal and masseter muscles. Histopathological examination demonstrated neoplastic cell invasion of temporal and masseter myofibers and of multiple peripheral nerves, including the trigeminal nerve. Central nervous system pathology consisted primarily of spinal root and leptomeningeal lymphoid cell infiltration with relative sparing of spinal cord and brain parenchyma.