Focal Peripheral Neuropathy Associated with Lymphoma in Dogs

Background : Peripheral neuropathies result in sensory, motor or autonomic dysfunctions due to impairment of peripheral spinal or cranial nerves. Neoplasms such as lymphoma are cited as one of the many aetiological causes and it may affect the nerve directly, by compression, or indirectly, or paraneoplastic, by remote action of the neoplasm located in an extra-neural site. This study aimed to report two cases of cranial nerve neuropathy (trigeminal and facial) associated with canine lymphoma, contributing to a better understanding of its paraneoplastic effects on the nervous system, as well as the diagnosis and treatment of these conditions. Cases: Two cases of canine lymphoma associated with possible signs of paraneoplastic peripheral neuropathy were attended at the Veterinary Hospital from the Universidade Federal de Minas Gerais (HV UFMG).  Case 1. A spayed mixed breed bitch, with lethargy and unilateral exophthalmos. Brain computed tomography revealed a retrobulbar mass and cytology was diagnostic for extranodal lymphoma. Subsequent to computed tomography, the dog was presented with hypotrophy of the facial musculature and difficulty in grasping food, consistent with trigeminal nerve palsy, which resolved after institution of the 19-week chemotherapy protocol from the University of Wisconsin. Nevertheless, disease reccurred and a rescue protocol was initiated. Case 2. A female Dalmatian, spayed, was diagnosed with multicentric lymphoma, after cytology of the left mandibular lymph node. Chemotherapy was initiated with the same protocol of the previous case. However, the disease progressed and it was observed facial asymmetry with ptosis of the left eyelid, pina and lips, in addition to difficulty in grasping food, suggesting facial and trigeminal cranial nerve palsy. Clinical signs resolved after institution of a rescue chemotherapy protocol. However, in both cases, disease progression and poor clinical condition resulted in decision of euthanasia and necropsy was not authorized. Discussion : Canine lymphoma is often associated with paraneoplastic syndromes, with neuropathy being one of its possible clinical manifestations. In spite of that its pathogenesis remains unclear, with little information in the veterinary literature. Diagnosis is challenging and must be initially based on recognition of neurological clinical signs and lesion localization, as in the reported cases with lesions located on the fifth and seventh cranial nerves. In the patient from the first case, the absence of clinical signs and laboratory abnormalities suggestive of endocrinopathies, associated with neurological signs restricted to the trigeminal nerve, bilaterally, before starting chemotherapy and without the identification of brain lesions in computed tomography, suggested paraneoplastic involvement as the cause of neuropathy. In the second case described, the absence of clinical signs and laboratory abnormalitiess suggestive of endocrinopathies or nutritional deficiencies, associated with neurological signs restricted to the facial and trigeminal cranial nerves, suggested direct or indirect tumour involvement. Both cases showed improvement of neurological clinical signs after chemotherapy which favored the therapeutic diagnosis. Nevertheless, failure to authorize necropsy of patients made it impossible to confirm that peripheral neuropathy is secondary to the remote effect of lymphoma.