Acute Trigeminal Nerve Neuritis in German Shepherd
Background: Trigeminal nerve is composed by ophthalmic, maxillary and mandibular portion, presenting sensory and motor functions. Its most common conditions include vascular, neoplastic, infectious and inflammatory causes. Neuritis is an inflammation caused by a primary nerve injury that can progress to demyelination and even degeneration of nerve fibers. The present report aims to describe an unusual case of a female dog, German Shepherd breed, with acute manifestation of trigeminal nerve neuritis whose etiology may be associated with erlichiosis, since infection with Ehrlichia spp. through serological test was verified.
Case: A 3-year-old female German Shepherd , weighing 26.8 kg and not neutered, was attended at Veterinary Hospital Dr. Halim Atique - UNIRP, São José do Rio Preto, SP, Brazil presenting apathy, sialorrhea and polydipsia for seven days. The tutor reported an episode of foamy and yellowish vomit three days ago and ixodidiosis last week. Physical examination revealed flaccid open-mouthed posture, with mild bilateral masseter and moderate temporal muscle atrophy. Water was offered to the animal and it was observed that it could not properly seize, confirming a false polydipsia. The neurological examination revealed a slight decrease in head sensitivity, difficulty in chewing and seizure of food. It was not observed alterations in the other pairs of cranial nerves or other neurological parameters (postural reactions and spinal reflexes), and the diagnose of bilateral dysfunction of the trigeminal nerve was based on the affected neuroanatomic region. On neurological examination, other lesions of the nervous system were ruled out, suggesting an isolated manifestation of the trigeminal nerve. CBC revealed anemia, intense thrombocytopenia and leukocytosis by neutrophilia. Radiographic examination ruled out the possibility of trauma due to the absence of mandible fracture and also temporomandibular joint alterations. Masseter and temporal muscle biopsy were performed, and myositis or other masticatory muscle alterations were discarded among the diagnostic possibilities. Serological tests showed non-reactive results for toxoplasmosis and neosporosis, but reagent for Erlichia spp.
Discussion: Idiopathic trigeminal neuritis (ITN) has an unknown etiology, but is not related to signs of systemic disease, and is usually not associated with deficits in other cranial nerves. The main clinical sign related to this condition is acute jaw paralysis, with inability to close the mouth, and in some cases is observed sensitivity deficits in face, as observed in the dog of this report during the neurological examination. In the patient of the present report, no justifiable causes were found for the presented symptoms, except the presence of erlichiosis. The treatment was based on the use of prednisone, doxycycline, antioxidants and vitamin complex. Response to treatment was satisfactory after seven days, and complete remission of clinical signs occurred nine days after its onset. Although cranial nerve neuritis is an uncommon clinical manifestation of erlichiosis, the patient in this study presented a good response to the treatment instituted, suggesting that erlichiosis is an important differential diagnosis for neuritis.
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