Pathological spontaneous activity as a prognostic marker in chronic inflammatory demyelinating polyneuropathy

Abstract

Background and purpose Monitoring of the disease course of patients with chronic inflammatory demyelinating polyneuropathy (CIDP) remains challenging because nerve conduction studies do not adequately correlate with functional disability. The prognostic value of pathological spontaneous activity (PSA) in needle electromyography (EMG) in different CIDP subgroups in a longitudinal context has, to date, not been analysed. We aimed to determine whether PSA was a prognostic marker or a marker of disease activity in a cohort of patients with CIDP. Methods A total of 127 patients with CIDP spectrum disorder were retrospectively analysed over 57 ± 47 months regarding the occurrence of PSA (fibrillations and positive sharp waves). The presence of PSA at diagnosis, newly occurring PSA, and continuously present PSA were longitudinally correlated with clinical disability using the Inflammatory Neuropathy Cause and Treatment Overall Disability Sum Score (INCAT‐ODSS) and CIDP subtype. Results Pathological spontaneous activity occurred in 49.6% of all CIDP patients at first diagnosis. More frequent evidence of PSA was significantly associated with a higher INCAT‐ODSS at the last follow‐up. Continuous and new occurrence of PSA were associated with higher degree of disability at the last follow‐up. The majority of patients with sustained evidence of PSA were characterized by an atypical phenotype, higher degree of disability, and the need for escalation of treatment. Conclusions Pathological spontaneous activity was associated with a higher degree of disability and occurred more frequently in atypical CIDP variants according to the longitudinal data of a large cohort of patients with CIDP. Our results showed that EMG examination was an adequate marker for disease progression and should be evaluated during the disease course.

Corneal inflammatory cell infiltration predicts disease activity in chronic inflammatory demyelinating polyneuropathy

“…Nevertheless, PSA might persist several months to years after axonal damage making it also not suitable as a dynamic biomarker. Thus, PSA can serve rather as a marker for disease progression in a long-term setting, as recently shown by our group 10 .…”

“…In contrast to CIC infiltration, PSA in EMG represents axonal damage. We have recently reported about PSA as a prognostic marker for CIDP patients in a long-term cohort study 10 . PSA is suitable to predict long-term clinical progression beyond 7 months 10 .…”

“…We have recently reported about PSA as a prognostic marker for CIDP patients in a long-term cohort study 10 . PSA is suitable to predict long-term clinical progression beyond 7 months 10 . We suppose that CIC infiltration represents an “active state” of inflammation, as it correlates to current disease activity, whereas over time, the correlation of CIC count and disease activity decreases.…”

“…The CIDP disease activity status (CDAS) is a simple score for clinical disease activity, however this score was validated to classify the long-term outcome and response to treatment in CIDP 7 . Established methods such as nerve conduction studies (NCS) can indicate disease progression but are often delayed 8 – 10 . In the chronic progressive disease phase, identification of an ongoing progression in NCS can be challenging due to a high degree of axonal damage.…”

“…In the chronic progressive disease phase, identification of an ongoing progression in NCS can be challenging due to a high degree of axonal damage. Electromyography (EMG) can detect pathological spontaneous activity (PSA), demonstrating denervation and axonal damage 10 . Nevertheless, PSA might persist several months to years after axonal damage making it also not suitable as a dynamic biomarker.…”