Nerve Conduction Studies of Dorsal Sural Nerve: Normative Data and Its Potential Application in ATTRv Pre-Symptomatic Subjects

Abstract

The objective of the study is to provide age-related normative values for dorsal sural nerve (DSN) and to analyse its application during follow-up of hereditary transthyretin amyloidosis (ATTRv) pre-symptomatic subjects. We consecutively recruited ATTRv pre-symptomatic carriers in which clinical examination, cardiological evaluation, and nerve conduction studies of the sural nerve and DSN were performed. To provide normative data of DSN, neurophysiologic parameters from healthy controls referred to our service were entered into linear regression analyses to check the relative influence of age and height. A correction grid was then derived. We collected 231 healthy subjects: the mean DSN sensory nerve action potential (SNAP) amplitude was 9.99 ± 5.48 μV; the mean conduction velocity was 49.01 ± 5.31 m/s. Significant correlations were found between age and height with DSN SNAP amplitude. Fifteen ATTRv pre-symptomatic carriers were examined. Sural nerve NCS were normal in 12/15 and revealed low/borderline values in three subjects. Considering our correction grid, we found an abnormal DNS amplitude in 9/15 subjects and low/borderline values in 2/15. In ATTRv, early detection of peripheral nerve damage is crucial to start a disease-modifying treatment. DSN may be easily and reliably included in the routine neurophysiological follow-up of ATTRv pre-symptomatic subjects.

Reference values for nerve conduction studies of the peroneal, tibial, and sural nerve derived from a large population‐based cohort: Associations with demographic and anthropometric characteristics—The Maastricht study

“…Sural nerve SNAP amplitudes were lower in our population, possibly due to the absence of younger participants 13 . However, the variation in data stratification and reported subgroups of the study population hampers a direct comparison to the values reported by Buschbacher et al and also to other reported reference values 14–20 . Moreover, difference in demographics of the study population, variation in study protocols, and other methodological factors limit the value of direct comparison 1 .…”

“…13 However, the variation in data stratification and reported subgroups of the study population hampers a direct comparison to the values reported by Buschbacher et al and also to other reported reference values. [14][15][16][17][18][19][20] Moreover, difference in demographics of the study population, variation in study protocols, and other methodological factors limit the value of direct comparison. 1 The percentage of absent sural nerve responses was comparable to percentages found by others, and a similar increase with age was seen.…”

Early detection of nerve involvement in presymptomatic TTR mutation carriers: exploring potential markers of disease onset

“…However, the segment routinely explored in daily practice is proximal to the sites initially affected by distal polyneuropathies. The study of the sural lateral dorsal cutaneous branch could overcome this limitation, therefore allowing early detection of peripheral nerve damage [ 27 , 31 , 39 ]. In our cohort, longitudinal conventional NCSs were able to detect sensory polyneuropathy as the first disease sign only in 2 cases.…”

“…NCSs of the DSN were performed in a subgroup of enrolled subjects having normal findings on conventional NCSs. Bilateral DSN was recorded antidromically, according to standard protocols [ 31 ].…”

“…Age- and sex-related normative values of our laboratory were used. The ratio between the SNAP amplitudes of the sural nerve and the DSN was also calculated, using a cut-off value of 4.17 [ 31 ]. We considered definitely pathological only those cases where both the age-/sex-adjusted DSN SNAP and the sural/DSN SNAP ratio were abnormal.…”