Prolonged distal motor latency of median nerve does not improve diagnostic accuracy for CIDP

Abstract

Compression of the median nerve at the carpal tunnel can give demyelinating features and result in distal motor latency (DML) prolongation fulfilling the EFNS/PNS demyelinating criteria for chronic inflammatory demyelinating polyneuropathy (CIDP). Accordingly, being carpal tunnel syndrome (CTS) common in the general population, the EFNS/PNS guidelines recommend excluding the DML of the median nerve when DML prolongation may be consistent with median neuropathy at the wrist from CTS. The main aims of this study were to verify whether the inclusion of DML of the median nerve (when consistent with CTS) could improve electrophysiological diagnostic accuracy for CIDP and if the median nerve at the carpal tunnel was more prone to demyelination. We analyzed electrophysiological data from 499 patients included consecutively into the Italian CIDP Database. According to the EFNS/PNS criteria, 352 patients had a definite, 10 a probable, and 57 a possible diagnosis of CIDP, while 80 were not fulfilling the diagnostic criteria. The inclusion of DML prolongation of median nerve did not improve significantly the diagnostic accuracy for CIDP; overall diagnostic class changed in 6 out of 499 patients (1.2%) and electrodiagnostic class of CIDP changed from not fulfilling to possible in only 2 patients (2.5% of not-fulfilling patients). In conclusion, we can infer that excluding DML prolongation of median nerve does not increase the risk of missing a diagnosis of CIDP thus corroborating the current EFNS/PNS criteria.

Motor Nerve Conduction Block Estimation in Demyelinating Neuropathies by Deconvolution

“…A retrospective study was performed on CIDP and MMN patients (followed from a clinical, electrophysiological and therapeutic point of view by D.C., following the normal clinical practice carried out at “I.R.C.C.S. Istituti Clinici Scientifici, S. Maugeri Foundation, Pavia, Italy”), which are part of a more relevant case series contained in the Italian CIDP Database and Italian MMN Database [ 7 , 27 ]. Diagnostic criteria were defined in [ 40 ] for CIDP and in [ 41 ] for MMN.…”

“…It is important to distinguish it from axonal loss, in which the axon is disrupted, so that its distal portion is no longer connected to the cell body and undergoes a process called Wallerian degeneration [ 5 ]. On the other hand, the lesions of the myelin sheaths (possibly caused by auto-antibodies against antigens at the node of Ranvier [ 6 ]) determine a slowing of AP propagation along the nerve (with abnormal temporal dispersion (TD) [ 7 ]) and sometimes the block of impulses (i.e., a CB [ 8 ]), reflected into muscle weakness. The methods routinely used in clinical practice for CB estimation are based on the comparison of the amplitudes or the areas of two compound muscle action potentials (CMAPs) elicited with transcutaneous electrical nerve stimulation at sites proximal and distal to the nerve segment in which the CB is suspected [ 4 , 9 ].…”

“…Thus, with the intent of extending the promising results shown in [ 19 ] to neuropathic patients with abnormal TD of the APs, in this paper SAW has been included in the deconvolution kernel. The method was then tested on experimental signals from both healthy subjects and pathological patients, with either Chronic Inflammatory Demyelinating Polyneuropathy (CIDP [ 1 , 7 , 26 , 27 , 28 , 29 , 30 ]) or Multifocal Motor Neuropathy (MMN [ 26 , 28 , 29 , 31 , 32 ]). Our results are expected to contribute to the discussion on guidelines [ 7 , 27 , 30 ] and the proposal of innovative methods for the assessment of CB [ 1 , 31 ].…”

“…The method was then tested on experimental signals from both healthy subjects and pathological patients, with either Chronic Inflammatory Demyelinating Polyneuropathy (CIDP [ 1 , 7 , 26 , 27 , 28 , 29 , 30 ]) or Multifocal Motor Neuropathy (MMN [ 26 , 28 , 29 , 31 , 32 ]). Our results are expected to contribute to the discussion on guidelines [ 7 , 27 , 30 ] and the proposal of innovative methods for the assessment of CB [ 1 , 31 ].…”