Abstract
BackgroundSevere carpal tunnel syndrome (CTS) readily lends itself to both clinical and electrophysiological recognition. The uncertainty sometimes is in identifying and quantifying motor involvement in mild and, perhaps, in moderate CTS. Our study aimed to evaluate F responses in mild and moderate CTS and determine the contribution of BMI to the F‐wave parameters.MethodsA retrospective review of the clinical and electrophysiological data of patients with CTS seen at the clinical neurophysiology laboratory of Aga Khan Hospital, Dar es Salaam, between 1 August 2017 and 31 July 2019 was retrieved. Carpal tunnel syndrome was graded according to the electrophysiological criteria of Padua. The F‐wave parameters of patients with mild‐to‐moderate CTS were analyzed and compared with asymptomatic controls.ResultWe studied 91 hands. Twenty‐two hands were asymptomatic controls, 30 hands had mild CTS, and 39 hands had moderate CTS. Patients with moderate CTS were more obese (p =.011), had more females (p =.044), and were older (p= <0.001). F‐wave parameters were not convincingly different between mild and moderate CTS. F‐wave chronodispersion (p =.035) and F‐wave persistence (0.019) were significantly different between nonobese control and mild and moderate CTS. Median–ulnar F‐wave latency difference (FWLD) was significant between obese patients with mild CTS and moderate CTS scores (p =.017).ConclusionAlthough a clear difference exists between F‐wave parameters in asymptomatic controls and those with CTS, the F‐wave study is inadequate in distinguishing mild and moderate CTS even in the context of BMI. Median–ulnar F‐wave latency difference (FWLD) appeared to be a promising discriminant parameter between obese patients with mild CTS and those with moderate CTS.
Highlights
F waves are late motor action potentials evoked in response to antidromic activation of motor neurons from the anterior horn cells. (Panayiotopoulos & Chroni, 1996) Since it assesses motor conduction along the whole length of a peripheral nerve, F-wave analysis is classically valuable in evaluating generalized neuropathy and the proximal segments of a peripheral nerve while providing a glimpse into the integrity of central motor conduction. (Fisher, 2007) its value in assessing focal neuropathies is questionable, F-wave anomalies have been demonstrated in focal neuropathies such as carpal tunnel syndrome (CTS). (Aalemdar, 2015; Aygül et al, 2014)
Anthropometric parameters such as height and BMI may influence nerve conduction parameters such as distal motor latency (DML) of the median nerve, and a prolonged F-wave minimal (F) latency of the tibial nerve lower sensory and mixed nerve amplitudes in healthy adults. (Buschbacher, 1998; Jerath & Shy, 2017) Aside from BMI, increasing age and the male gender correlated with decreasing amplitude and area values (Buschbacher, 1999) and the nerve conduction velocities. (Awang et al, 2007) Height is known to correlate with median F-wave minimum latency directly. (Aalemdar, 2015; Puksa et al, 2003)
Clinical severity and grading of CTS have been suggested to have a direct correlation with prolonged F latency. (El et al, 2017) Other parameters from conventional electrodiagnostic studies such as median motor terminal latency index (m TLI), median motor residual latency, and median– ulnar F-wave latency difference (F diff MU) have been suggested as potentially useful data. (Park et al, 2014) these parameters have not been proven to add any additional diagnostic benefit to the existing conventional electrodiagnostic studies for carpal tunnel syndrome. (Mondelli & Aretini, 2015)
Summary
F waves are late motor action potentials evoked in response to antidromic activation of motor neurons from the anterior horn cells. (Panayiotopoulos & Chroni, 1996) Since it assesses motor conduction along the whole length of a peripheral nerve, F-wave analysis is classically valuable in evaluating generalized neuropathy and the proximal segments of a peripheral nerve while providing a glimpse into the integrity of central motor conduction. (Fisher, 2007) its value in assessing focal neuropathies is questionable, F-wave anomalies have been demonstrated in focal neuropathies such as carpal tunnel syndrome (CTS). (Aalemdar, 2015; Aygül et al, 2014). (Aalemdar, 2015; Aygül et al, 2014) Anthropometric parameters such as height and BMI may influence nerve conduction parameters such as distal motor latency (DML) of the median nerve, and a prolonged F-wave minimal (F (min)) latency of the tibial nerve lower sensory and mixed nerve amplitudes in healthy adults. Clinical severity and grading of CTS have been suggested to have a direct correlation with prolonged F (min) latency. (El et al, 2017) Other parameters from conventional electrodiagnostic studies such as median motor terminal latency index (m TLI), median motor residual latency (mRL), and median– ulnar F-wave latency difference (F diff MU) have been suggested as potentially useful data. This study aimed to evaluate F-wave parameters in mild and moderate CTS while unraveling BMI's contribution to the F- wave parameters
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