TABLE 1.
Clinical presentation of the main ICI-related peripheral neurological syndromes
| Myositis (Kao et al., 2017; Suzuki et al., 2017; Johansen et al., 2019; Kadota et al., 2019; Psimaras et al., 2019; Dubey et al., 2020) | MG (Romi et al., 2012; Gonzalez et al., 2017; Makarious et al., 2017; Kao et al., 2018; Takamatsu et al., 2018; Knauss et al., 2019; Farrugia and Goodfellow 2020) | GBS (Dalmau et al., 2017a; Dubey et al., 2018; Vogrig et al., 2019c; Wesley and Ferguson 2019) | |
|---|---|---|---|
| Incidence (% patients treated with ICIs) | 1% | – | 0.1%–0.3% |
| Clinical presentation | Myalgia and axial weakness, dropped head (usually symmetrical) | Fluctuating weakness and fatigability of proximal muscles and ocular and bulbar muscles | Hypoesthesia/hyporreflexia and distal motor deficit |
| Frequently diplopia and ptosis | Generalized MG; rapid onset and progression to severe forms | Cranial nerve involvement | |
| Possible respiratory failure | Frequent overlap with myositis (50%–93%) | Neuropathic pain | |
| Overlapping with myocarditis (25%) | Myocarditis also possible (11%) | Respiratory involvement exceptionally reported | |
| Laboratory test | Elevated CK, troponin T, and transaminases (troponin I more specific of cardiac involvement) | Frequent overlapping with myositis with elevated CK (50.93%) | Anti-ganglioside antibodies rarely positive (12%) |
| Specific myositis antibodies are generally negative | Anti-AChR antibodies detected in 53%–87% cases | Cerebrospinal fluid analysis with elevated proteins and mild lymphocytic pleocytosis | |
| ENMG and imaging | Majority of patients (70%–100%) show a myopathic pattern with positive sharp waves. Less frequent reduced CMAPs (50%) | Repetitive nerve stimulation with single fiber shows a decremental response and increased jitter (50%–97%) | Demyelinating pattern with prolonged F-wave latencies and decreased conduction velocities |
| PET and CT show contrast-enhanced areas on post-contrast images. MRI with hyperintense intramuscular alterations on T2 and TI inversion images and contrast capitation in T1 | Less frequently shows a mixed or axonal pattern | ||
| MRI can expose contrast enhancement of cranial nerves or spinal roots | |||
| Other diagnostic workup | Biopsy: focal infiltrates with necrotic pattern and T-cell infiltration | Edrophonium and icepack tests sometimes positive | – |
| CD4+ and CD8+ in variable proportion. CD68+ cells present | |||
| Rare appearance of CD20+ cells |
MG: myasthenia gravis. GBS: Guillain-Barré syndrome. ENMG: electroneuromyogram.