A Case of Cervical Intramedullary Dirofilaria immitis Associated with Nerve Sheath Tumor in a Dog

Dirofilaria immitis, a globally widespread nematode known for its high mortality rate, primarily infests the cardiovascular system, notably the pulmonary artery and right ventricle. However, since 1856, instances of adult heartworm infestation in atypical sites have been documented, including the eye, peritoneal cavity, subcutaneous region, skeletal muscle, systemic arteries, and the central nervous system (CNS). Dirofilariasis often manifests asymptomatically, but severe cases can lead to respiratory and circulatory complications, even sudden death. Migration of D. immitis to the CNS results in symptoms corresponding to the parasite's location rather than typical heartworm signs. Magnetic resonance imaging (MRI) plays a crucial role in diagnosing CNS parasitic infestations, aiding in lesion evaluation and parasite localization. Additionally, malignant peripheral nerve sheath tumors (MPNSTs), originating from Schwann cells, fibroblasts, and perineural cells, are rare neoplasms with high recurrence rates and poor prognoses. While MPNST metastases are infrequent, they have been reported in various animal species and anatomical sites, including the CNS. Here, we present the first documented case of intramedullary D. immitis associated with a nerve sheath tumor in a dog, highlighting the unique intersection of parasitic infestation and neoplastic disease in veterinary medicine.