Meng-Ni  Wu

CASE REPORT:
A 43-year-old man with HGBL who could function independently presented with numbness and weakness of the left thigh 2 months after a diagnosis of infiltrative lymphoma in the left psoas muscle. His symptoms were urine incontinence and unsteady gait. A neurological examination revealed weakness in the left psoas and quadriceps with hyporeflexia and hypesthesia. Lumbar spine magnetic resonance imaging (MRI) revealed intraspinal extradural invasion from T12 to L3 with multiple left-sided root compression despite the resolution of primary psoas lymphoma. At 6 weeks after symptom onset, his symptoms progressed to weakness, numbness, and hyporeflexia of the bilateral lower extremities with preserved anal sensation. Follow- up MRI revealed the progression of intraspinal invasion, which spread through the spinal canal and invaded the contralateral neural foramina from T12 to L3. The patient was finally bound to a wheelchair.

DISCUSSION:
NHL is the most common type of lymphoma, and B-cell lymphoma accounts for most of the cases of NHL. HGBL, a newly established category in the 2016 World Health Organization (WHO) classification, replaces the previous category of B-cell lymphoma with indistinguishable features between diffuse large B-cell lymphoma and Burkitt lymphoma. HGBL with MYC and BCL2 expression is termed double-hit lymphoma, and the involvement of the central nervous system is frequently observed with relapse. Patients with HGBL have an aggressive clinical course and exhibit a poor response to standard chemotherapy regimens. Even high-dose chemotherapy or autologous stem-cell transplantation does not improve outcomes. The median overall survival is 1.5 years 2, 3. The skeletal muscles are rarely involved in NHL (a phenomenon reported in only 1.1% of patients). Because of the rarity of muscle involvement in HGBL, related data are not available. In NHL, the extremities, pelvis, and gluteal regions are the most commonly affected muscles, and the psoas muscle is rarely involved1. Epidural spinal cord compression occurs in 0.1% to 6.5% of patients with NHL, and the thoracic spine is the most commonly affected (followed by the lumbar and cervical spine). Patients with lymphoma involving the epidural space typically exhibit preceding paraspinal soft-tissue involvement and subsequent invasion into the epidural space through the intervertebral foramina without bone destruction, as observed in our case 4. To the best of our knowledge, although NHL usually invades the epidural space through the intervertebral foramina, the infiltration of NHL spreading through the spinal canal with the involvement of the bilateral intervertebral foramina has not been reported. In critically ill patients, paraparesis may mislead the clinician to consider it a neuropathy related to critical illness. Moreover, in patients with initial intraabdominal lymphoma, the asymmetric involvement of the bilateral lower legs may be misdiagnosed as bilateral plexopathy. We highlight the importance of determining the possible spinal canal involvement in patients with NHL with bilateral neurological deficits, particularly for those with known paraspinal soft-tissue involvement. Furthermore, adjacent soft tissue or neurological involvement cannot be excluded based on the resolution of initial lymphoma. Compared with CT, MRI provides better resolution for separating the normal tissue from the abnormal soft tissue5. In our case, abdominal CT revealed the resolution of mass in the left psoas muscle, whereas MRI revealed the epidural invasion of lymphoma from the intervertebral foramina. Therefore, we suggest MRI, instead of CT, for follow-up in patients with NHL with paraspinal soft-tissue involvement. Surgery, radiotherapy, or a combination of both are therapeutic options for spinal cord compression by lymphoma. Surgical intervention can be simultaneously used for obtaining a tissue specimen and decompression. However, prior studies have reported no significant difference in the outcome between combination with decompressive laminectomy and radiotherapy and spinal radiation only. Typically, NHL is a chemo- sensitive tumor, and chemoradiotherapy may provide a favorable outcome, except for HGBL, which is a chemoresistant tumor6. Pretreatment neurologic status, especially motor function, is the most crucial prognostic factor for overall survival and functional outcome 7. Unfortunately, the patient was finally discharged without surgical intervention because of difficulty in isolating and decompressing nerve roots after the tumor encroaches the spinal cord with bilateral multilevel foraminal invasion. In conclusion, we reported a rare case of HBGL where it infiltrated the left psoas muscle before spreading through the spinal canal and subsequently invading the contralateral intervertebral foramina from T12 to L3. Clinicians must identify any possible encroachment to the spinal canal in patients with HBGL, particularly patients with known paraspinal soft-tissue involvement. The resolved infiltration of the soft tissue cannot preclude the possibility of neurological involvement. Additionally, MRI may provide higher resolution findings for clarifying the structure of the neural foramina and thecal sac.