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.     

Multicentric nerve sheath fibrosarcomas of multiple cranial nerve roots in two dogs

Nerve sheath fibrosarcomas of the left 5th through 8th cranial nerve roots were diagnosed in 1 dog and of the left 4th through 8th cranial nerve roots in another dog. Clinical signs in both dogs included head tilt to the left, circling to the left, left hemiparesis and proprioception deficits, rotary nystagmus, left-sided atrophy of masticatory muscles, and cutaneous hypalgesia of the left side of the face. Cranial nerve roots from both dogs were incorporated in discrete, firm, encapsulated, lobulated, tan masses of various sizes that compressed adjacent brain stem and cranial nerves. There were no regional or distant metastases; however, there was enlargement of nerve roots adjacent to the masses. The masses were composed of bundles and sheets of anaplastic, polymorphic to spindle-shaped cells that infiltrated cranial nerves and ganglia and extended into the brain along nerve roots. Masses contained various amounts of collagen and reticulin fibers, but no mucopolysaccharide ground substance. There was no myelin or S-100 protein associated with neoplastic cells. The tumors appeared to have a multicentric origin from cranial nerve sheaths.     

Neurohistologic and ultrastructural lesions in cattle experimentally intoxicated with the plant Prosopis juliflora

Intoxication by pods of Prosopis juliflora (mesquite beans) causes an impairment of cranial nerve function in cattle and goats. In goats, vacuolation of neurons in the trigeminal motor nuclei has been reported. To study the lesions in cattle caused by consumption of P. juliflora pods and dry ground pods, eight 6- to 12-month-old male cattle were divided into 4 groups: group 1 was fed a ration containing 50% of pods; groups 2 and 3 received a ration containing 50 and 75% of dry ground pods, respectively; group 4 was the control. After 200 days, all cattle were killed and sampled for histologic evaluation. Samples of the trigeminal motor nucleus were examined by electron microscopy. All cattle from groups 1, 2, and 3 showed clinical signs resulting from impaired function of cranial nerves V, IX, X, and XII, starting 45-75 days after consumption of the plant. The main histologic lesions were vacuolation and loss of neurons in trigeminal motor nuclei and other motor cranial nerve nuclei with Wallerian-like degeneration in the cranial nerves. Mild denervation atrophy was observed in the masseter and other masticatory muscles. On electron microscopy, neurons of the trigeminal nuclei had markedly swollen mitochondria, with the mitochondrial cristae displaced peripherally, disoriented and disintegrating. Intoxication by P. juliflora seems to have a novel pathogenesis, characterized by a selective, primary, chronic, and progressive injury to mitochondria of neurons of the trigeminal and other cranial nerve nuclei. Cranial nerve degeneration and denervation atrophy of the muscles occurs as a consequence of the neuronal lesion.     

Highly invasive intracranial malignant schwannoma in a rat

A highly invasive intracranial malignant schwannoma containing several masses was detected in a 28-week-old male Crl:CD(SD) rat. Macroscopically, 3 masses were noted in the cranial cavity; one was present at the bottom of the cranial cavity and involved the trigeminal nerve, and the other two were in the parietal bone. Histologically, each mass consisted of fusiform cells with interlacing fascicular, wavy and nuclear pseudopalisading arrangements and round cells with cystic lesions. The tumor cells invaded not only the brain but also the parietal bone. In the brain, the tumor cells infiltrated diffusely into the leptomeningeal and perivascular spaces and parenchyma, in which the tumor cell morphology and invasive pattern closely resembled those of malignant astrocytoma and malignant reticulosis. Immunohistochemically, the tumor cells in the masses showed positive reactions for both S-100 protein and GFAP, while those in the cerebral invasion sites were negative for GFAP and less positive for S-100 protein. Electron microscopically, a single basal lamina layer and short intricate cell processes were confirmed in the tumor cells. From these results, the present tumor was diagnosed as a malignant schwannoma arising in the cranial cavity, probably originating from the trigeminal nerve. The present tumor is considered to be a relatively unique malignant schwannoma based on its growth and invasion patterns.     

Studies on the pathogenesis of pseudorabies in domestic cats following oral inoculation.

Domestic cats were inoculated orally with an Iowa isolate of pseudorabies virus. Several cats were killed at intervals of one day and tissues were examined virologically and histologically to determine the initial sites of virus penetration and replication and to evaluate the pathways traveled by the virus from the mouth to the central nervous system. Lesions were consistent in the tonsils, along the pathways of the sensory branches of the ninth and tenth cranial nerves, the tractus and nucleus solitarius and the area postrema in the medulla. Less consistent lesions in the ganglia and nuclei of the fifth cranial nerve indicated a lesser role for the passage of virus via this nerve. Nervous lesions consisted of multifocal to diffuse microgliosis, mononuclear perivascular cuffing and a mononuclear inflammatory cell infiltration with a variable number of neutrophils occasionally forming microabscesses. Virus isolations correlated well with microscopic lesions. Ultrastructurally, virions were observed within the nucleus of the neurons in the medulla. Clinical signs were similar to those previously reported. Pruritus was consistently absent. Virus was isolated consistently for the first two or three days postinoculation from oral and nasal secretions but not from secretions after three days.     

Extramedullary plasmacytoma in a horse with ptyalism and dysphagia.

A Clydesdale mare was examined for weight loss, inappetence, ptyalism, and dysphagia. The main abnormality revealed by serum biochemistry was a marked hyperglobulinemia, and protein electrophoresis revealed a monoclonal gammopathy in the gamma region. The urine was positive for Bence Jones proteins. These findings suggested a plasma cell tumor. The neoplasm could not be located with extensive antemortem examination. At postmortem, neoplastic cells morphologically compatible with plasma cells and positive for equine IgG with imunoperoxidase staining infiltrated the pericardium, mediastinal stromal tissues, adrenal glands, meninges, atrioventricular valves, aorta, abdominal and thoracic fat, and nerves, including the trigeminal nerve. The neoplastic cells invading the cranial nerves were responsible for many of the presenting signs.     

Macro anatomical investigations of the cranial cervical ganglion in domestic pig (Sus scrofa domesticus)

In this study, the left and right cranial cervical ganglia (ganglion cervicale craniale) of eight young (four male, four female) domestic pigs weighing around 70-80 kg were inspected macro anatomically. The cranial cervical ganglion (CCG) was found cranio-ventrally of the distal ganglion of the vagus nerve, medial of the jugular process extremity, ventral of the atlas, dorsal of the epiglottis base and medial of the common root (CR) established by the internal carotid and occipital arteries. The internal carotid nerve and jugular nerve ramified from the cranial part of CCG. The jugular nerve gave branches that merged with the vagus and glossopharyngeal nerves. Other nerve branches originating from the cranial part of the ganglion reached to the external carotid artery and CR. The internal carotid nerve varied among cadavers in number of branches (two to four). These branches did not travel along the side of the internal carotid artery. The central part of CCG gave thin nerve branches that reached to various anatomical structures including the first and second cervical nerves, wall of the pharynx, accessory nerve, hypoglossal nerve, vagus nerve, external carotid artery and CR. The caudal part of CCG gave nerve branches that merged with the vagus, cranial laryngeal nerves, and common carotid artery. The external carotid nerves, which were two or three in number, also originated from the caudal part of CCG. In conclusion, the nerves ramifying from CCG of the pig varied in number among cadavers. Compared with literature raised in other species, there are also differences in number of nerve branches and course pattern of these nerves.     

Electrically elicited blink reflex in horses with trigeminal and facial nerve blocks

OBJECTIVE: To reassess reference values for the components of the electrically induced blink reflex, document reference values for facial motor nerve conduction velocity, and demonstrate usefulness of the blink reflex as a diagnostic tool in peripheral facial and trigeminal nerve dysfunction in horses. ANIMALS: 10 healthy adult horses (8 males, 2 females) without neurologic abnormalities. PROCEDURE: Blink reflex tests were performed by electrical stimulation of the supraorbital nerve and facial (auriculopalpebral) nerve. Reflex and direct muscle-evoked potentials of the orbicularis oculi muscles were recorded from concentric needle electrodes inserted bilaterally in these muscles. Supraorbital and auriculopalpebral nerve blocks were performed by lidocaine hydrochloride injections. RESULTS: Supraorbital nerve stimulation elicited 2 or 3 ipsilateral and 1 contralateral reflex muscle potential in the orbicularis oculi muscles. Auriculopalpebral nerve stimulation elicited a direct and a reflex potential in the ipsilateral orbicularis oculi muscle. After left supraorbital nerve block, no responses could be elicited ipsilaterally or contralaterally upon stimulation of the blocked nerve, but bilateral responses were obtained upon stimulation of the right supraorbital nerve. After right auriculopalpebral nerve block, no responses were recorded from the right orbicularis oculi muscle upon stimulation of left or right supraorbital nerves. CONCLUSIONS AND CLINICAL RELEVANCE: Reference values for the components of the blink reflex and facial motor nerve conduction velocity will allow application of these tests to assist in the diagnosis of equine neurologic disorders involving the trigeminal and facial nerves, the brainstem, and the cranial end of the cervical segment of the spinal cord. This study reveals the usefulness of the blink reflex test in the diagnosis of peripheral trigeminal and facial nerve dysfunction in horses.     

Effects of high dietary sulfur on brain functions using evoked potentials technique.

Brain stem auditory-evoked response (BAER) is a noninvasive technique used for detecting neurophysiological abnormalities of the brain stem along the auditory pathway. Brain stem auditory-evoked response recordings were obtained from subcutaneous skin electrodes from two control sheep and 22 other sheep fed high sulfur (S) diets with low or high concentration of thiamine (B1), copper (Cu), and molybdenum (Mo). At least four peaks (I,II,III,IV) of varied amplitude were observed in all animals. Neurophysiological abnormalities due to decreased conductivity and/or excitability of nerve fibers along the auditory pathway were found on the BAER recordings of sheep fed high S diet. Abnormalities of peaks and interpeak latencies within BAER recordings were related to histopathological observations of brain stem lesions. Lesions in the areas of the cochlear nuclei and lateral lemniscus were seen in conjunction with altered BAER components. However, abnormalities in BAER recordings and lesions in the brain stem also occurred in the absence of overt clinical signs. Analysis of interpeak latencies between peaks I and IV revealed significant differences among dietary groups. Sheep given diets low in Cu, Mo, and B1 were affected most. Factorial analysis indicated B1 and interactions among Cu, Mo, and B1 as significant factors influencing interpeak latencies.     

Ovine listerial encephalitis: analysis, hypothesis and synthesis

Analysis of field data suggested that listerial encephalitis in sheep was most common in winter and early spring in the age groups of sheep which would be cutting, changing and possibly losing teeth. It was hypothesised that under these conditions ingested Listeria monocytogenes could reach the fine dental terminals of the trigeminal nerve causing an ascending neuritis and encephalitis. Experimental inoculation of organisms into the dental pulp demonstrated the feasibility of this route of infection. Histological encephalitis was evident six days after inoculation but the incubation period to clinical neurological disease was at least three weeks.     

Lesions and retroviruses associated with naturally occurring ovine pulmonary carcinoma (sheep pulmonary adenomatosis)

Five sheep with ovine pulmonary carcinoma were markedly dyspneic and had sporadic coughing; two had copious watery nasal exudate. In four, lesions consisted of multifocal nodules of neoplastic cuboidal epithelial cells in acinar or papillary patterns. Electron microscopically, cells had microvilli, tight junctions, and cytoplasmic lamellar bodies typical of alveolar type II cells. One sheep had a single lung tumor of nonciliated bronchiolar epithelial cells. Vacuolated alveolar macrophages surrounded adenomatous foci. One sheep had a metastatic lesion in the caudal mediastinal lymph node. All sheep had histologic lesions of lymphoid interstitial pneumonia (LIP, ovine progressive pneumonia) consisting of peribronchiolar and interstitial lymphoid hyperplasia, and fibromuscular proliferation; all had serum precipitating antibodies to ovine lentivirus. Lung fluids or tumor homogenates contained a 26-kd peptide that crossreacted with a primate-derived type D retrovirus as detected by immunoblotting or interspecies competition radioimmunoassay. Ovine lentivirus was isolated from concentrated lung fluids or tumor tissues of four sheep tested and from tumor cell DNA of one animal transfected into ovine muscle cells. These studies document the presence of type D-related retrovirus antigen in ovine pulmonary carcinoma (OPC) in the United States and indicate that lentivirus-induced LIP is a lesion frequently associated with this disease.     

Cauda equina neuritis: a chronic idiopathic polyneuritis in two horses

Two cases of cauda equina neuritis are compared and contrasted. Neurological deficits of the tail and perineum were noted and functional deficits were seen in gait, urination, defecation and cranial nerve function. Lesions consisted of nonsuppurative inflammation of the nerve trunks and proliferation of the perineurium of the cauda equina. Cranial nerve involvement in one case supported a diagnosis of polyneuritis equi rather than cauda equina neuritis. The possible etiologies and pathogenesis of this disease are discussed.     

Clinical application of multidetector computed tomography and magnetic resonance imaging for evaluation of cranial nerves in horses in comparison with high resolution imaging standards

Although horses are affected by cranial nerve disease, our understanding of these structures' imaging anatomy is limited, and the optimal modality for imaging of each of these nerves is unclear. The aim of this study was to describe the imaging appearance of the equine cranial nerves on high‐resolution 1.5T magnetic resonance imaging (MRI) and computed tomography (CT) scans of a cadaver head, and with these as standards, examine the utility of MRI and CT performed in clinical cases. High‐resolution MRI and CT images were prospectively acquired of the head of a normal Thoroughbred gelding following euthanasia. Ten clinical cases undergoing high‐field MRI under general anaesthesia and 10 clinical cases undergoing CT in the standing horse under sedation were retrospectively evaluated by three reviewers to assess cranial nerve visibility. On high‐resolution, thin‐slice, MRI scans of the normal cadaver head, each of the 12 cranial nerves and their topographic location could be appreciated. On high‐resolution cadaver CT, cranial nerves II, V and VII were clearly visible, but others were less easily identified; osseous structures were clearly visualised. Clinical MRI and CT allowed for variable visualisation of the cranial nerves, dependent on the sequence and the orientation of scan planes. High‐field MRI allowed excellent visualisation of equine cranial nerves, whereas CT allowed for more detailed visualisation of the osseous canals and foramina. In live horses, the ability to identify all 12 nerves is challenging with either MRI or CT; however, high‐field MRI enables better visualisation of the nerve bundles than CT.     

Detection of Mycobacterium paratuberculosis antigen with colloidal immunogold in naturally infected sheep.

The anti-Mycobacterium paratuberculosis polyclonal serum is proved useful for labelling Mycobacterium paratuberculosis in glutaraldehyde-osmium-fixed and epon-embedded intestinal samples from sheep with clinical symptoms of paratuberculosis. M. paratuberculosis marked with antibody-coated colloidal gold stain was seen in macrophages, epithelioid cells, giant cells and neutrophils throughout intestinal mucosa. In large macrophages with a low lysosomal content, a great number of intact mycobacteria was seen within phagosomes. In macrophages with average lysosomal content, very few intact mycobacteria or mycobacterial debris were present and lysosome-phagosome fusions were observed. Mycobacteria within neutrophils were scanty. These results show the usefulness of colloidal immunogold techniques for studies of the pathogenesis of paratuberculosis.     

Gliomatosis cerebri in six dogs

Gliomatosis cerebri is a well-recognized entity in human medicine characterized by unusually widespread infiltration of the neuraxis by neoplastic glial cells with relative preservation of brain architecture. This report describes the pathologic features of the disease in six dogs. The dogs ranged from 3 to 9 years of age (mean 6.1 years) without evidence of breed predilection; five of the six dogs were neutered or intact males. The clinical findings were mixed (including depression, circling, cranial nerve deficits), reflecting the diffuse nature of the disease. Histologically, there was remarkably diffuse infiltration of the white and gray matter of the brain by small numbers of elongated neoplastic cells. Areas of greater cellularity formed grossly visible lesions in four cases. Anisocytosis and pleomorphism were greater in areas of higher cellularity. Other features of tumor growth included subpial accumulation, neuronal satellitosis, perivascular cuffing, and tropism for cranial nerve and brain stem nuclei. Neoplastic cells were negative on immunohistochemical stains for glial fibrillary acid protein (GFAP) and leukocyte markers, reflecting the uncertain histogenesis of these unusual neoplasms.     

Headshaking in horses: possible aetiopathogenesis suggested by the results of diagnostic tests and several treatment regimes used in 20 cases

Twenty mature horses with typical headshaking of 2 week-7 year duration were studied. Clinical examinations included radiography of the head and nasopharyngeal endoscopy. All were assessed at rest and at exercise, both before and after fitting an occlusive nasal mask, application of tinted contact lenses and the perineural anaesthesia of the infraorbital and posterior ethmoidal branches of the trigeminal nerve. Infraorbital anaesthesia had no effect in 6/7 cases but 11/17 (65%) cases showed a 90-100% improvement following posterior ethmoidal nerve anaesthesia. Tinted contact lenses had no apparent long-term benefit, although 2 cases showed a transient improvement. We found no other evidence to suggest a photic aetiology in the current series of cases. Treatment regimens based on the results of the diagnostic investigative methods included sclerosis of the posterior ethmoidal branch of the trigeminal nerve. This was effective in some cases but the benefits were temporary. Cyproheptadine alone was ineffective but the addition of carbamazepine resulted in 80-100% improvement in 80% of cases. Carbemazepine alone was effective in 88% of cases but results were unpredictable at predefined dose rates. The positive response to carbamazepine, combined with the clinical features is consistent with involvement of the trigeminal nerve, particularly the more proximal branches such as the posterior ethmoidal nerve. Headshaking has some clinical features in common with trigeminal neuralgia in humans. As a result of the findings detailed in this paper, we conclude that a trigeminal neuritis or neuralgia may be the basis of the underlying aetiopathology of equine headshaking. Initial observations of the positive response of headshakers to carbamazepine therapy is encouraging. However, future studies will include a more detailed investigation of dosages, duration of effectiveness (in some cases it appears short-lived) and other effects. In practice there is a realistic possibility of controlling but not curing headshaking with carbamazepine therapy at the present time. Other future investigations will include details of the functional anatomy of the trigeminal nerve and the role of the P2 myelin protein in headshaking and other neurological disease.     

Magnetic resonance imaging anatomy of the rabbit brain at 3?T

Background

Rabbits are widely accepted as an animal model in neuroscience research. They also represent very popular pet animals, and, in selected clinical cases with neurological signs, magnetic resonance imaging (MRI) may be indicated for imaging the rabbit brain. Literature on the normal MRI anatomy of the rabbit brain and associated structures as well as related reference values is sparse. Therefore, it was the purpose of this study to generate an MRI atlas of the normal rabbit brain including the pituitary gland, the cranial nerves and major vessels by the use of a 3 T magnet.

Results

Based on transverse, dorsal and sagittal T2-weighted (T2w) and pre- and post-contrast 3D T1-weighted (T1w) sequences, 60 intracranial structures were identified and labeled. Typical features of a lissencephalic brain type were described. In the 5 investigated rabbits, on T1w images a crescent-shaped hyperintense area caudodorsally in the pituitary gland most likely corresponded to a part of the neurohypophysis. The optic, trigeminal, and in part, the facial, vestibulocochlear and trochlear nerves were identified. Mild contrast enhancement of the trigeminal nerve was present in all rabbits. Absolute and relative size of the pituitary gland, midline area of the cranial and caudal cranial fossa and height of the tel- and diencephalon, 3rd and 4th ventricles were also determined.

Conclusions

These data established normal MRI appearance and measurements of the rabbit brain. Results provide reference for research studies in rabbits and, in rare instances, clinical cases in veterinary medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-015-0139-6) contains supplementary material, which is available to authorized users.     

Xanthomatosis in geckos: five cases.

Five cases of xanthomatosis in geckos were evaluated, one in a northern green gecko (Naultinus grayi) and the remaining four in three species of leaf-tailed geckos (two Uroplatus henkeli, one U. sikorae, one U. fimbriatus). All geckos were females 3-11 yr of age, were clinically ill on presentation, and either died or were euthanized. Necropsies showed emaciation in three geckos, with white nodular foci on coelomic surfaces in two of these geckos. The other two geckos had no gross abnormalities. Histopathologic examination revealed xanthomatosis involving the coelomic surfaces of four geckos and the ventricles of the brain in all geckos. Xanthomas in the brain were associated with various degrees of hydrocephalus. The lesions were comprised of stacks of clear clefts consistent with cholesterol crystals, and these structures were surrounded by epithelioid macrophages, multinucleated giant cells, and lymphocytes. Four geckos had active folliculogenesis, and two had foci of follicular degeneration and localized yolk coelomitis. In all cases, xanthomatosis was believed to have contributed significantly to morbidity and mortality.     

Increased phosphorylation of c-Jun NH (2)-terminal protein kinase in the sciatic nerves of Lewis rats with experimental autoimmune neuritis

The phosphorylation of c-Jun NH (2)-terminal protein kinase (JNK), one of the mitogen-activated protein kinases, was analyzed in the sciatic nerves of Lewis rats with experimental autoimmune neuritis (EAN). Western blot analysis showed that the expression levels of both phosphorylated JNK1 (p-JNK1, approximately 46 kDa) and phosphorylated JNK2 (p-JNK2, approximately 54 kDa) in the sciatic nerves of rats with EAN increased significantly (p < 0.05) at day 14 post-immunization (PI) and remained at this level at days 24 and 30 PI, with a slight decrease. In EAN-affected sciatic nerves, there was intense immunostaining for p-JNK in the infiltrating inflammatory cells (especially ED1-positive macrophages) and Schwann cells on days 14-24 PI, compared with those of controls. Some macrophages with increased p-JNK immunoreactivity was shown to be apoptotic, while some Schwann cells remained survived in this rat EAN model, suggesting that JNK is differentially involved in the EAN-affected sciatic nerves. These findings suggest that JNK phosphorylation is closely associated with the clearance of inflammatory cells as well as the activation of Schwann cells in the EAN affected sciatic nerves.