[Age-related changes in amplitude ratio, duration ratio and area ratio in nerve conduction studies].
We investigated the effect of aging on nerve conduction parameters in 184 subjects (aged 10-75 years) without any history or signs of peripheral neuropathy, in order to clarify the diagnostic parameters of demyelinating neuropathies in the aged. The CMAP amplitude ratio (proximal CMAP/distal CMAP), duration ratio and area ratio remained unchanged throughout the second to eighth decades. The lower limits of normal CMAP amplitude ratio (mean -3SD) were 0.79 (median nerve), 0.74 (ulnar nerve), 0.59 (peroneal nerve), and 0.48 (tibial nerve). The upper limits of normal CMAP duration ratio (mean 11+ 3SD) were 1.22 (median nerve), 1.19 (ulnar nerve), 1.35 (peroneal nerve), and 1.32 (tibial nerve). The lower limits of normal CMAP area ratio (mean -3SD) were 0.84 (median nerve), 0.78 (ulnar nerve), 0.61 (peroneal nerve), and 0.62 (tibial nerve). There were no age-related changes in amplitude ratio or duration ratio of SNAP, although the standard deviations increased with age. Since the amplitude ratio, duration ratio and area ratio are simple and age-independent, they can provide useful and reliable information for routine nerve conduction studies for aged patients with demyelinating neuropathies.
Third Department of Internal Medicine, Hiroshima University School of Medicine.
K
K
Kurokawa
E
E
Tanaka
H
H
Yamashita
T
T
Nakayama
H
H
Maruyama
M
M
Yukawa
T
T
Kohriyama
Y
Y
Mimori
S
S
Nakamura
D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002648:Child; D003711:Demyelinating Diseases / Q000175:diagnosis; D006801:Humans; D008875:Middle Aged; D009132:Muscles / Q000502:physiology / Q000503:physiopathology; D009431:Neural Conduction; D010525:Peripheral Nerves / Q000502:physiology* / Q000503:physiopathology