Murthy Nikhil K, Amrami Kimberly K, Broski Stephen M, Johnston Patrick B, Spinner Robert J
1Department of Neurosurgery, Mayo Clinic, Rochester.
2Department of Radiology, Mayo Clinic, Rochester; and.
J Neurosurg Spine. 2021 Oct 1;36(3):464-469. doi: 10.3171/2021.4.SPINE21344. Print 2022 Mar 1.
Neurolymphomatosis (NL) is a rare manifestation of lymphoma confined to the peripheral nervous system that is poorly understood. It can be found in the cauda equina, but extraspinal disease can be underappreciated. The authors describe how extraspinal NL progresses to the cauda equina by perineural spread and the implications of this on timely and safe diagnostic options.
The authors used the Mayo Clinic medical records database to find cases of cauda equina NL with sufficient imaging to characterize the lumbosacral plexus diagnosed from tissue biopsy. Demographics (sex, age), clinical data (initial symptoms, cerebrospinal fluid, evidence of CNS involvement, biopsy location, primary or secondary disease), and imaging findings were reviewed.
Ten patients met inclusion and exclusion criteria, and only 2 of 10 patients presented with cauda equina symptoms at the time of biopsy, with 1 patient undergoing a cauda equina biopsy. Eight patients were diagnosed with diffuse large B-cell lymphoma, 1 with low-grade B-cell lymphoma, and 1 with mantle cell lymphoma. Isolated spinal nerve involvement was identified in 5 of 10 cases, providing compelling evidence regarding the pathophysiology of NL. The conus medullaris was not radiologically involved in any case. Lumbosacral plexus MRI was able to identify extraspinal disease and offered diagnostically useful biopsy targets. FDG PET/CT was relatively insensitive for detecting disease in the cauda equina but was helpful in identifying extraspinal NL.
The authors propose that perineural spread of extraspinal NL to infiltrate the cauda equina occurs in two phases. 1) There is proximal and distal spread along a peripheral nerve, with eventual spread to anatomically connected nerves via junction and branch points. 2) The tumor cells enter the spinal canal through corresponding neural foramina and propagate along the spinal nerves composing the cauda equina. To diffusely infiltrate the cauda equina, a third phase occurs in which tumor cells can spread circumdurally to the opposite side of the spinal canal and enter contralateral nerve roots extending proximally and distally. This spread of disease can lead to diffuse bilateral spinal nerve disease without diffuse leptomeningeal spread. Recognition of this phasic mechanism can lead to identification of safer extraspinal biopsy targets that could allow for greater functional recovery after appropriate treatment.
神经淋巴瘤（NL）是局限于周围神经系统的淋巴瘤的一种罕见表现，目前对此了解甚少。它可出现在马尾，但脊柱外疾病可能未得到充分认识。作者描述了脊柱外NL如何通过神经周围扩散进展至马尾以及这对及时和安全的诊断选择的影响。
作者利用梅奥诊所的医疗记录数据库查找有足够影像学资料以对经组织活检诊断的腰骶丛进行特征描述的马尾NL病例。回顾了人口统计学资料（性别、年龄）、临床数据（初始症状、脑脊液、中枢神经系统受累证据、活检部位、原发性或继发性疾病）及影像学表现。
10例患者符合纳入及排除标准，10例患者中仅2例在活检时出现马尾症状，其中1例接受了马尾活检。8例患者被诊断为弥漫性大B细胞淋巴瘤，1例为低级别B细胞淋巴瘤，1例为套细胞淋巴瘤。10例中有5例发现孤立性脊神经受累，为NL的病理生理学提供了有力证据。在任何病例中，脊髓圆锥在影像学上均未受累。腰骶丛MRI能够识别脊柱外疾病并提供有诊断价值的活检靶点。FDG PET/CT对检测马尾疾病相对不敏感，但有助于识别脊柱外NL。
作者提出脊柱外NL经神经周围扩散浸润马尾分两个阶段。1）沿周围神经向近端和远端扩散，最终通过连接点和分支点扩散至解剖学上相连的神经。2）肿瘤细胞通过相应的椎间孔进入椎管并沿构成马尾的脊神经扩散。为了弥漫性浸润马尾，会发生第三阶段，即肿瘤细胞可沿椎管周围扩散至对侧并进入向近端和远端延伸的对侧神经根。这种疾病扩散可导致弥漫性双侧脊神经疾病而无弥漫性软脑膜扩散。认识这种阶段性机制可有助于识别更安全的脊柱外活检靶点，从而在适当治疗后实现更好的功能恢复。
