2. Compound nerve action potential (CNAP) study is a useful examination for evaluating muscle afferent Ia fibers

Abstract

s of the 40th Annual Meeting of Japanese Society of Clinical Neurophysiology, Kobe, Japan, November 1–2, 2010 Ryuji Kaji , Koichi Hirata b,⇑ a Secretariat: Koishikawa Building 4F, 5-3-13 Otsuka, Bunkyo-ku, Tokyo 112-0012, Japan, Department of Neurology, Dokkyo Medical University, 880 Kitakobayashi, Mibu, Shimotsuga, Tochigi 321-0293, Japan 1. Traumatic injury of the digital nerve by snow shoveling—Rie Haga, Chieko Murakami, Masayuki Baba (Aomori Prefectual Central Hospital, Aomori, Japan) We presented a case with traumatic injury of the median palmar digital nerve by snow shoveling. A woman aged 74 visited us for three month-history of numbness and dysesthetic pain in the left index finger and thumb after snow shoveling. On examination, there was hypoesthesia on the palm side of the left index finger and thumb. Tinel sign was positive by percussion to the upper edge of the thenar eminence. The left median motor conduction to the abductor pollicis brevis muscle was normal. Compound sensory action potentials recorded from the left thumb and the index finger were around 5 lV, both distinctively reduced compared with those from the left middle and ring fingers, 27 and 18 lV, respectively. Inching records of the sensory potential from the index finger by electric stimulation with successive decrement by one cm from the wrist demonstrated prolonged conduction time more than 0.7 ms at the particular segment including the Tinel sign point: all other segments had normal conduction time of around 0.3 ms. These findings indicated the focal demyelination and Wallerian degeneration at the site of the injury. doi:10.1016/j.clinph.2011.01.013 2. Compound nerve action potential (CNAP) study is a useful examination for evaluating muscle afferent Ia fibers—Keisuke Abe, Tadashi Kanouchi, Teruhiko Sekiguchi, Hidehiro Mizusawa, Takanori Yokota (Tokyo Medical and Dental University, Tokyo, Japan) The aim of this study was to investigate whether CNAP is useful tool for evaluation of Ia fiber conduction. The conventional sensory nerve conduction study recording the sensory nerve action potential (SNAP) gives us the information of only the cutaneous afferents but not about the muscle afferents. We tried to use CNAP of the median nerve for evaluating muscle afferent. The median nerves of seven patients with sensory neuropathy and 4 normal subjects were studied. CNAPs was clearly recorded in all patients with inexcitable SNAP as well as normal subjects. The velocity of CNAP was faster than those of SNAP and CMAP (compound muscle action potential) in the same segment in all normal subjects. The CNAPs in three of 5 patients with no SNAP evoked were obviously faster than the CMAPs. In three patients whose SNAP was evoked, the CNAPs were the fastest among the three responses. Because the conduction velocity of CNAP is determined by that of Ia fiber in normal subjects, CNAP study has the potential to evaluate Ia fiber conduction. Furthermore, in patients with severe sensory neuropathy showing inexcitable SNAP, CNAP study is expected to be an only and new examination for sensory nerve function. doi:10.1016/j.clinph.2011.01.014 3. Comparison in placement location of disposable surface electrode in antidromic sensory nerve conduction study—Kenji Sekiguchi, Toko Miyawaki, Mariko Takata, Akihiro Nomura, Ichiro Yokota, Yoshihisa Otsuka, Naoko Yasui, Horotoshi Hamaguchi, Hisatomo Kowa, Fumio Kanda, Tatsushi Toda (Department of Neurology, Kobe University, Kobe, Japan) Although the ring electrodes generally used in antidromic sensory nerve conduction study of hand, disposable surface electrode is frequently used in recent years and there are many advantages in terms of infection control and usability. However, there are no reports of investigation in optimal location of electrode placement. Antidromic median nerve sensory conduction study was performed in 20 hands of 10 healthy subjects. We made comparison with each measurement of disposable surface electrodes placed at various locations and ring electrodes. The latency and the amplitude delivered by disposable surface electrode placed on midline volar aspect of index finger showed no significant difference compared to using a ring electrodes. In case of surface electrode placement on the radial aspect of index finger, lower amplitude and shorter latency were doi:10.1016/j.clinph.2011.01.012 ⇑ Corresponding author. Tel.: +81 282 87 2152; fax: +81 282 86 5884. E-mail address: hirata@dokkyomed.ac.jp (K. Hirata). Clinical Neurophysiology 122 (2011) e9–e14