Dorsal sural nerve conduction study in vitamin B₁₂ deficiency with megaloblastic anemia

Abstract

Peripheral neuropathy is frequently observed in B(12) deficiency. In spite of this, there is little knowledge about peripheral neuropathy in B(12) deficiency because the severity of clinical involvement of the central nervous system clearly outweighs signs and symptoms due to peripheral nervous system involvement. We primarily investigated peripheral neuropathy with dorsal sural conduction study, which is a new method for detection of early peripheral neuropathy, in B(12) deficiency with megaloblastic anemia. Conventional nerve conduction studies and tibial sensory-evoked potential (SEP) recording were also performed. Twenty-eight B(12)-deficient patients (15 male, 13 female, mean age 65.8 years) with megaloblastic anemia and 18 age- and sex-matched controls were included in the study. Although dorsal sural sensory nerve action potentials (SNAPs) were not recorded in 15 (54%) of 28 patients, only 9 (32%) of them were found to have polyneuropathy by conventional conduction studies. Furthermore, patients with dorsal sural SNAP had mean lower amplitude, mean longer latency, and slower velocity response when compared with controls. Twenty patients (71%) were diagnosed as having myelopathy by the combination of tibial SEP and neurological findings. Two patients whose dorsal sural SNAPs were not recorded had normal tibial SEP responses; therefore, these patients were considered to have isolated peripheral neuropathy. As a result, we conclude that dorsal sural nerve conduction study is a reliable method for detection of early peripheral neuropathy in B(12) deficiency.

Dorsal sural sensory nerve action potential: A study for reference values

“…[2610111213] Similarly, in the present study, dorsal sural response could be obtained in all the participants, the oldest participant being 90 years old. In two participants who had a callus below and behind the lateral malleolus, the SNAP was difficult to obtain, and the study was abandoned.…”

“…In a study of dorsal sural conduction in megaloblastic anemia, absent responses were found in 54% patients whereas remaining patients had mean lower amplitude, longer latency, and slower conduction velocity as compared to healthy control participants. [13] This signified the importance of cutoff values of dorsal sural conduction to identify early peripheral neuropathy rather than relying on the mere presence or absence of dorsal sural SNAP. The present study on dorsal sural conduction defined important cutoff values for lower limit of normal for amplitude and velocity in three age groups in western Indian population.…”

“…[1112] Higher sensitivity of dorsal sural conduction to Vitamin B12 deficiency and megaloblastic anemia has also been documented. [13] Reference values for nerve conduction parameters are influenced by age and anthropometric measurements. [14151617] There is scarcity of normative data and anthropometric comparisons of dorsal sural sensory action potential.…”

Vitamin B-12 treatment of asymptomatic, deficient, elderly Chileans improves conductivity in myelinated peripheral nerves, but high serum folate impairs vitamin B-12 status response assessed by the combined indicator of vitamin B-12 status

“…We observed improvements in sensory nerve conduction in the lower extremities. The sensory fibers are usually the first to be affected by vitamin B-12 deficiency (15,16) and an evaluation of sural nerve function has been suggested as an early indicator of peripheral nerve deterioration (29). The neurophysiologic evaluation of our participants also included QST and SSEPs, but no changes were observed in these variables after the vitamin B-12 injection, possibly because an improvement in vitamin B-12 status affects mainly large afferent peripheral nerves rather than the smaller fibers.…”

“…Sensory polyneuropathy is also observed in vitamin B-12 deficiency (8) and involves myelinated large-caliber afferent fibers (7,8). Although the clinical and neurophysiologic features of symptomatic vitamin B-12 deficiency in patients with neurologic manifestations have been reported (6,9), most reports have been from case studies of elderly subjects with pernicious anemia who received a variety of treatments and different followup assessments (10)(11)(12)(13) or have only studied small groups of participants (7,(14)(15)(16). It is not well established whether impairments in neurologic function occur in population groups with poor vitamin B-12 status but no clinical symptoms of deficiency (17) or whether changes in function can be achieved through vitamin B-12 supplementation.…”