Primary peripheral nerve lymphoma: a case report and literature review.

Neurolymphomatosis (NL) is an uncommon malignant lymphoma characterized by selective infiltration of the central and peripheral nervous system. In this case report, we present a patient diagnosed with diffuse large B-cell lymphoma who initially manifested with peripheral neuropathy, primarily characterized by weakness of the left lower limb. By exploring its clinical manifestations, ancillary tests, and reviewing the relevant literature, we aim to deepen our understanding, diagnosis, and treatment of this disease. A 48-year-old male patient presented to the Department of Neurology, Hematology, and Neurosurgery with complaint of left lower limb weakness that had persisted for over 11 months. Initial laboratory tests and cerebrospinal fluid analysis yielded negative results. Electromyography examination indicated damage to the left lumbar plexus and iliac plexus nerves raising suspicions of nerve root involvement. Enhanced MRI of the lumbosacral plexus nerves revealed thickening and enhanced signals in left nerve roots at T12-L1, L1-2, and L3-4 levels. Additionally, local thickening and enhancement of signals were observed in the left erector spine muscle, psoas major, and iliopsoas muscles compared to the contralateral side. PEC/CT imaging displayed multiple soft tissue density shadows in the left foraminal area at the T12-1 and L1-2 levels. Bone marrow examination excluded hematological disease. Subsequent biopsy of the left foraminal nerve root at T12-L1 and the vertebral muscle at L3 level confirmed a diagnosis of diffuse large B-cell malignant lymphoma, indicating PNSL due to the involvement of multiple nerve roots. Following diagnosis, the patient underwent chemotherapy, resulting in the alleviation of his symptoms. Diagnosing PNSL can be challenging due to the nonspecific clinical manifestations and often inconclusive laboratory test results. Misdiagnosis and delayed diagnosis are common pitfalls. Electromyography may reveal damage to the affected peripheral nerves, while MR imaging might show nerve root thickening, and PET/CT can demonstrate increased lesion uptake. However, the definitive diagnosis relies on a biopsy of the lesion. Treatment for PNSL typically involves chemotherapy.