Review of the Diagnostic Challenges of Lambert–Eaton Syndrome Revealed Through Three Case Reports

Autonomic dysfunction detected by skin sympathetic response in Lambert-Eaton myasthenic syndrome: a case report

Background

Lambert-Eaton myasthenic syndrome (LEMS) is a type of paraneoplastic syndrome that may initially manifest itself with proximal weakness and gait abnormalities. Approximately up to 50% of LEMS patients have a primary autonomic dysfunction.

Case presentation

We present here a case of a 75-year-old male with symmetric proximal muscle weakness, dry mouth and constipation. The cutaneous response to scratch and upright tilt-table testing were positive. A repetitive nerve stimulation test showed that there was a decremental response of compound muscle action potential (CMAP) amplitude at 3 Hz while an incremental response at 20 Hz. The presence of antibodies against voltage-gated calcium channels (VGCC) confirmed the diagnosis. Because of the prominent symptom of autonomic disorder, the patient further underwent the test of skin sympathetic response (SSR). Lower amplitude and longer response duration were found in palms, while it evoked no response in soles.

Conclusions

In this case, we present the detailed results of SSR test on a patient suffering LEMS with autonomic disorder. Since autonomic dysfunction has a significant impact on clinical management and SSR test is an effective detection method, we recommend that SSR test be performed on patients with LEMS regularly.

A Case of Triple-Negative Myasthenia Gravis Lambert-Eaton Overlap Syndrome With Negative Agrin and LRP-4 Antibodies

A case of triple-negative myasthenia gravis Lambert-Eaton overlap syndrome with negative Agrin and LRP-4 antibodies. Myasthenia gravis (MG) is an autoimmune disorder that shares similar features with Lambert-Eaton myasthenic syndrome. The combined clinical and electrophysiological findings of MG and Lambert-Eaton myasthenic syndrome have been reported, these cases represent the so-called "myasthenia gravis Lambert-Eaton overlap syndrome" (MLOS). A total of 55 MLOS cases have been identified, 13 cases were reported before the acetylcholine receptor (AChR) antibody (ab) testing era, 14 during the AChR-ab era, 26 during the voltage-gated calcium channel (VGCC)-ab era, and 2 cases have been reported during the muscle-specific kinase (MuSK)-ab era, of these; only 1 patient tested negative for all 3 antibodies. New immunological markers have been identified in the study of MG [Agrin and the low-density lipopro-tein receptor-related protein 4 (LRP-4)]. We present a patient with MLOS who tested negative for all 5 (AChR, MuSK, VGCC, Agrin, and LRP-4) serologic markers.

Retrospective study of paraneoplastic neurological syndromes in a Chinese Han population from Shandong, East China

OBJECTIVE

To analyze the clinical features, diagnostic strategies and therapeutic methods associated with paraneoplastic neurological syndromes.

METHODS

A retrospective study of paraneoplastic neurological syndromes was performed at a single center in Shandong, East China. The medical records and follow-up data of 28 patients were intensively reviewed between February 2011 and December 2014.

RESULTS

Twenty-four (85.7%) patients experienced subacute or chronic onset of disease, and the most common symptoms reported were mild myasthenia and paresthesias. Twenty-five (89.3%) patients presented nervous system lesions prior to occult tumors, and the median time frame between paraneoplastic neurological syndromes onset and the diagnosis of a tumor was 15 weeks. Sensorimotor neuropathy, Lambert-Eaton myasthenic syndrome and limbic encephalitis were the three most common neurological syndromes reported. Elevated serum tumor markers were observed in 44.0% of patients, while 40.7% of patients were positive for onconeural antibodies. Tumors were detected in 21 (75.0%) patients after repeated whole-body screening, and lung carcinomas were the most common primary tumor detected. Seventeen patients received anti-tumor or immunological therapy, and clinical symptoms were relieved in 13 (76.5%) of these patients.

CONCLUSIONS

In the majority of paraneoplastic neurological syndromes patients, the onset of disease is subacute or chronic with mild clinical symptoms. Nervous system lesions usually occur prior to occult tumors with complicated and various clinical manifestations. Neither tumor markers nor onconeural antibodies exhibit a high rate of occurrence, while repeated whole-body screening is helpful in identifying occult tumors. Early diagnosis and treatment are crucial to these patients.