title: Sural/radial amplitude ratio in the diagnosis of mild axonal polyneuropathy.
abstract: As proximal nerves are relatively spared in length-dependent, axonal polyneuropathy, we theorized that a sural/radial amplitude ratio (SRAR) might be a sensitive indicator of mild polyneuropathy. In this study, sural amplitudes and SRARs in patients with signs of mild axonal polyneuropathy were compared to those of normal, age-matched control subjects. Sural and radial sensory responses were measured in a standard fashion in all subjects. Thirty polyneuropathy patients had an average SRAR of 0.29 as compared to 0.71 for the 30 normal subjects. An SRAR of less than 0.40 was a strong predictor of axonal polyneuropathy, with 90% sensitivity and 90% specificity, as compared to an absolute sural amplitude of less than 6.0 microV, which had sensitivity of only 66%. Additionally, unlike the sural amplitude, the ratio did not vary significantly with age. We conclude that the SRAR is a sensitive, specific, age-independent electrodiagnostic test for mild axonal polyneuropathy.
authors.affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Rutkove
authors.forename: M J
authors.initials: MJ
authors.lastname: Kothari
authors.forename: E M
authors.initials: EM
authors.lastname: Raynor
authors.forename: M L
authors.initials: ML
authors.lastname: Levy
authors.forename: R
authors.initials: R
authors.lastname: Fadic
authors.forename: R A
authors.initials: RA
authors.lastname: Nardin
mesh_terms: D000328:Adult; D000368:Aged; D001369:Axons / Q000502:physiology*; D004568:Electrodiagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D011826:Radial Nerve / Q000503:physiopathology*; D012016:Reference Values; D013497:Sural Nerve / Q000503:physiopathology*; D013997:Time Factors