Submaksimal Uyarimla Elde Edilen Iki Tepeli Ortodromik Duysal Yanitlarin Hastalik Süreçlerine Yönelik Elektrofizyolojik Incelemelerde Kullanilmasi/Double Peak Orthodromic Sensory Responses in the Electrophysiological Examination of Pathological Conditions

ÖZET. Amaç: Submaksimal uyarimla elde edilen çift tepeli ortodromik duysal yanitlar henüz hasta gruplari üzerinde çalisilmamistir. Bu yöntemle elde edilen ikinci yanit tepesinin anodal uyarimla ortaya çiktigi ve en distal sinir liserinden kaynaklandigi ileri sürülmektedir. Bu çalismada klinik olarak ve standart sinir iletim incelemeleri ile polinöropati bulgusu olmayan iki diyabetli hasta grubunda çift tepeli ortodromik duysal yanitlar arastirildi. Yöntemler: Çalismamiza bozuk glukoz toleransi (BGT) olan 20 hasta, tip 2 diyabetes mellitusu (DM) olan 14 hasta ve 25 saglikli gönüllü alindi. Dominant olmayan tarafta motor iletim incelemelerine ek olarak median sinirde ortodromik çift tepeli duysal yanitlar, ortodromik duysal aksiyon potansiyelleri (DAP), sural/radiyal amplitüd orani ve medial plantar sinir DAP çalisildi. BGT ve DM hastalari Michigan Diyabetik Nöropati Skalasi ile degerlendirildi. Bulgular: DM grubunda median sinir duysal distal latansi uzun ve ulnar sinir duysal aksiyon potansiyeli amplitüdü düsük bulundu. Çift tepeli ortodromik duysal yanit incelemesinde uyari esigi ve maksimal uyari siddeti, BGT ve DM gruplarinda kontrollerden yüksekti. DM grubunda birinci tepe ve ikinci tepe latanslarinda uzama saptandi. Sonuç: Bu çalismada çift tepeli duysal yanitlarin erken diyabetik polinöropati tanisinda standart elektroSzyolojik testlere üstünlügünü gösteren bulgu saptanmadi. Ancak çalismanin polinöropati ile uyumlu yakinmalari olan, elektroSzyolojik incelemeleri normal olan gruplarda tekrarlanmasinin uygun olacagi düsünüldü. Buna karsilik duysal esiklerde saptanan farkliliklar nedeniyle, güvenilirligi test edildigi taktirde, esik belirleme yönteminin erken polinöropati tanisi için umut verici oldugu kanisi edinildi. Bu çalismada elde edilen elektroSzyolojik bulgular, genel olarak erken dönemde ve iyi kontrol altinda olan diyabetiklerde bile polinöropatinin baslamis oldugunu göstermekteydi. (Nöropsikiyatri Arsivi 2010; 47: 338-43). Anahtar kelimeler: Polinöropati, bozuk glukoz tolerans testi, diyabetes mellitus, diyabetik polinöropati. ABSTRACT. Objective: Double peak sensory responses elicited with submaximal stimulation is an electrophysiological method that has not been studied previously in pathological conditions. The second peak of the response was claimed to be produced by anodal stimulation and originated from the most distal regions of the nerve fibers. The objective of the study was to test double peak sensory responses in two groups of diabetic patients in two different stages of the disease. Methods: Conventional nerve conduction studies performed in 20 patients with impaired glucose tolerance (IGT), 14 with type 2 diabetes mellitus (DM), and in 25 healthy control subjects revealed normal results. Orthodromic double peak sensory responses with submaximal stimulation of the median nerve, sural/radial amplitude ratio and medial plantar nerve orthodromic sensory nerve action potentials (SNAP) were also studied in the non-dominant side. IGT and DM patients were evaluated with the Michigan Diabetic Neuropathy Scale (MDNS). Results: The mean median nerve sensory distal latency was prolonged and ulnar SNAP amplitude was significantly reduced in DM patients compared to the subjects in the other two groups. DM and IGT patients had higher stimulation thresholds and maximal stimulation intensities than the control subjects. The latencies of the first and second components of the double peak sensory responses were also prolonged in the DM group compared to the other groups. Conclusion: This study did not reveal any result indicating that double peak sensory responses with submaximal stimulation were superior to conventional nerve conduction studies in the detection of early diabetic polyneuropathy. However, the number of subjects included in our study is insufficient for a final decision on this matter, and further studies are needed to include diabetic patients having clinical signs and symptoms of polyneuropathy and normal nerve conduction studies. Stimulation threshold assessment might be a promising tool for the detection of early nerve involvement, if its reproducibility is achieved. This study showed once more that peripheral neuropathy may develop in individuals with diabetes even in early stage and with good glycemic control. (Archives of Neuropsychiatry 2010; 47: 338-43). Key words: Polyneuropathy; Impaired glucose tolerance, diabetes mellitus, diabetic polyneuropathy.

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