LEMS is not simply another form of myasthenia gravis
Both diseases impair neuromuscular transmission, but LEMS is a presynaptic disorder most often associated with antibodies against P/Q-type VGCCs. The current German S2k guideline describes a typical triad of proximal exercise-related weakness, hypo- or areflexia and autonomic symptoms such as dry mouth, sweating changes, constipation, erectile dysfunction or orthostatic complaints. The distinction matters because diagnostic testing, cancer screening and treatment differ from myasthenia gravis.
P/Q-type VGCC antibodies are a central diagnostic test
The German guideline reports P/Q-type VGCC antibodies in about 85% of patients with LEMS. Antibody results should be interpreted with the clinical pattern and electrophysiology rather than used as a stand-alone diagnosis. SOX1 antibodies can add information when paraneoplastic LEMS is suspected but do not replace imaging-based tumor screening.
Electrophysiology should look for the characteristic increment
LEMS typically produces a low initial compound muscle action potential (CMAP), a decrement on low-frequency repetitive stimulation and a marked increment after brief maximal contraction or high-frequency stimulation. A specialist neurophysiology review is particularly useful when earlier testing was labelled nonspecific or when the differential includes myasthenia gravis, neuropathy or motor-neuron disease.
Tumor screening is part of the LEMS work-up
The current German guideline recommends active tumor search because small-cell lung cancer can appear after the neurological syndrome. It recommends thoracic CT for all patients with LEMS and, when that is negative, FDG-PET/CT, followed by risk-adapted repeat screening. This is especially important in older patients and current or former smokers, but the guideline does not limit initial screening only to high-risk patients.
Amifampridine is the main authorised symptomatic treatment
EMA authorises Firdapse (amifampridine) and a generic amifampridine product for symptomatic treatment of LEMS in adults. Therapy should be initiated under a physician experienced in LEMS. Dose titration, seizure risk, QT/cardiac considerations, renal or hepatic impairment and interacting medicines must be reviewed individually; this is not an over-the-counter strength treatment.
Pyridostigmine can be considered as an adjunct in selected patients
The German guideline notes that pyridostigmine may be combined with amifampridine based on expert practice and can sometimes help dry mouth as well as neuromuscular symptoms. It should not be assumed to work in LEMS exactly as it does in myasthenia gravis.
Paraneoplastic LEMS requires effective cancer treatment
When LEMS is associated with small-cell lung cancer or another tumor, the neurological pathway and oncology pathway must be coordinated. The German guideline states that treatment of the underlying tumor is the primary focus for paraneoplastic LEMS, while effective symptomatic amifampridine can be continued. International travel should therefore be organized around an integrated oncology-neurology plan rather than a neurology-only package.
Immunotherapy is selected, not automatic
For insufficient response to symptomatic treatment, the German guideline discusses immunotherapy such as corticosteroids with a steroid-sparing agent and notes evidence for IVIG. The decision depends on whether LEMS is idiopathic or paraneoplastic, tumor treatment, severity, comorbidities and long-term prognosis. IVIG or immunosuppression should not be marketed to every patient with weakness before diagnosis is secure.
Autonomic symptoms deserve active review
Dry mouth, constipation, erectile dysfunction, sweating abnormalities and orthostatic symptoms are common enough to be diagnostically useful and can affect quality of life. A second opinion should document these features along with muscle strength and gait rather than focusing only on limb weakness.
What to send for a German LEMS second opinion
A remote review is most useful when the receiving team can see both neuromuscular evidence and the tumor-screening history.
- P/Q-type VGCC antibody and SOX1 antibody results if performed
- Repetitive nerve stimulation / EMG reports including CMAP and increment data
- Neurology or myasthenia-clinic reports
- Thoracic CT, FDG-PET/CT and oncology records
- Smoking history and prior cancer history
- Current amifampridine/Firdapse dose and response
- ECG and relevant cardiac history
- Current medicines for interaction review
- Previous IVIG or immunotherapy and response
- A specific question: confirm LEMS, distinguish from MG, optimize amifampridine, review tumor screening or immunotherapy
Rapid severe weakness or breathing/swallowing deterioration needs local care first
Stable LEMS can be reviewed internationally, but severe new breathlessness, inability to swallow safely, aspiration concern, marked rapidly progressive weakness or another acute deterioration requires urgent local assessment and stabilization before medical travel.
Official sources
Sources last checked 2026-09-02. Clinical pathways, eligibility and hospital procedures can change; confirm current requirements directly with the treating center.
- S2k guideline: diagnosis and treatment of myasthenic syndromes — German Society of Neurology / DGM ↗
- Lambert-Eaton myasthenic syndrome — German Society for Muscular Diseases (DGM) ↗
- Firdapse EPAR — European Medicines Agency ↗
- Charité myasthenic syndromes / LEMS — Charité – Universitätsmedizin Berlin ↗
- Freiburg myasthenia and LEMS clinic — University Medical Center Freiburg ↗
- Heidelberg myasthenic disorders — Heidelberg University Hospital ↗