Alhammad Reem M, Alshamlan Yafa, Alneseyan Ruwa, Al-Harbi Talal M, Alhijab Ali, Alanazy Mohammed H
Department of Internal Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
Department of Neurology, King Fahad Specialist Hospital, Dammam, Saudi Arabia.
Front Neurol. 2024 Dec 13;15:1525155. doi: 10.3389/fneur.2024.1525155. eCollection 2024.
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of the presynaptic neuromuscular junction associated with antibody mediated dysfunction of voltage-gated calcium channels (VGCCs). LEMS can exist as a paraneoplastic syndrome, paraneoplastic-LEMS (P-LEMS), when associated with tumors, most commonly, small cell lung carcinoma (SCLC) or as a non-paraneoplastic condition (NP-LEMS) when no malignancies are detected.
A retrospective chart review was conducted in 3 tertiary hospitals in Saudi Arabia for patients diagnosed with LEMS between January 2010 and January 2020. Patients meeting all the following criteria were included: (1) weakness or fatigability of one or more extremity or oculo-bulbar muscles, (2) 60% or higher increment of compound muscle action potential (CMAP) amplitudes immediately following isometric exercise, and (3) positive serum P/Q type VGCC antibodies. Clinical, laboratory, and electrophysiologic features, as well as radiologic imaging modalities performed for tumor screening were reviewed.
The study included six patients diagnosed with LEMS, split evenly between P-LEMS and NP-LEMS. Fatigability, particularly in the lower extremities, and dyspnea on exertion were commonly reported symptoms. Low CMAP amplitudes were more frequently seen in NP-LEMS as compared to P-LEMS when recorded from both abductor pollicis brevis and abductor digiti minimi muscles. An incremental response above 60% in post activation CMAPs was detected at similar rates following variable durations of isometric exercise (10, 15, and 20 s). Tumor types detected in 3 patients with P-LEMS are SCLC, breast carcinoma, colon adenocarcinoma, and prostate acinar adenocarcinoma. Triple malignancy was detected in one patient.
This is the first study to describe clinical and electrophysiologic features of LEMS in an Arab ethnic cohort. Early recognition of LEMS has a significant impact on prognosis, especially given the aggressive nature of associated cancers such as SCLC.
兰伯特 - 伊顿肌无力综合征（LEMS）是一种突触前神经肌肉接头的自身免疫性疾病，与电压门控钙通道（VGCCs）抗体介导的功能障碍相关。当与肿瘤相关时，LEMS可表现为副肿瘤综合征，即副肿瘤性LEMS（P - LEMS），最常见的是与小细胞肺癌（SCLC）相关；当未检测到恶性肿瘤时，则表现为非副肿瘤性疾病（NP - LEMS）。
对沙特阿拉伯3家三级医院2010年1月至2020年1月期间诊断为LEMS的患者进行回顾性病历审查。纳入符合以下所有标准的患者：（1）一个或多个肢体或眼外肌肌无力或易疲劳；（2）等长运动后复合肌肉动作电位（CMAP）幅度立即增加60%或更高；（3）血清P/Q型VGCC抗体阳性。对临床、实验室和电生理特征以及用于肿瘤筛查的影像学检查方式进行了回顾。
该研究纳入了6例诊断为LEMS的患者，P - LEMS和NP - LEMS各占一半。易疲劳，尤其是下肢易疲劳，以及运动时呼吸困难是常见症状。从拇短展肌和小指展肌记录时，与P - LEMS相比，NP - LEMS中CMAP幅度较低更为常见。在不同时长（10、15和20秒）的等长运动后，激活后CMAP增加超过60%的反应发生率相似。3例P - LEMS患者检测到的肿瘤类型为SCLC、乳腺癌、结肠腺癌和前列腺腺泡腺癌。1例患者检测到三重恶性肿瘤。
这是第一项描述阿拉伯族裔队列中LEMS临床和电生理特征的研究。早期识别LEMS对预后有重大影响，特别是考虑到相关癌症如SCLC的侵袭性。
