Publication: Siyatik sinir hasarının beyin somatosensoriyel korteksindeki fonksiyonel değilimler üzerindeki etkisi
Abstract
Periferik sinir sistemi; otonomik fonksiyonların idamesi, duyuların merkezi sinir sistemine iletimi ve merkezi sinir sisteminden motor fonksiyonlara yönelik bilgilerin kas ve eklemlere iletiminden sorumludur. Periferik sinir hasarı morbiditesi yüksek olan bir hastalık durumudur. Hasar sonrası tedavi süreci planlanırken, hasarın makro ve mikro düzeydeki durumu göz önünde bulundurulur. Mikro düzeyde incelendiğinde 3 tip hasar mevcuttur. Nöroprakside akson ve çevre destek doku sağlamdır. Sadece fonksiyonel kayıp söz konusudur. Cerrahi tedavi gerekmeden haftalar içerisinde sinir eski durumunu kazanır. Aksonotmezisde sadece akson yapısal hasar görmüştür, ağır formlarında cerrahi gereklidir. Nörotmezisde hem akson hem de destek doku hasar görmüştür ve cerrahi müdahale gerekir. Makro düzeyde ise sinir hasarının gerçek etkisi geç dönemde ortaya çıkabilir. Bu nedenle cerrahi müdahalenin bu gibi bir durumda daha geç bir dönemde yapılmasının fonksiyonel kazanımı arttırdığı saptanmıştır. Periferik sinir hasarının tedavisindeki süreç çeşitli elektro-tanısal ve görüntüleme teknikleri ile izlenebilmektedir. Fakat, periferik sinir hasarı sonrasında bu sistemle devamlı bağlantı içinde olan ve duysal geri-bildirimler alıp, ona uygun besleyici cevaplar veren merkezi sinir sisteminin, özellikle somatosensoriyel korteksin nasıl etkilendiği hakkında çeşitli elektro-tanısal yöntemler kullanılsa da yeterli miktarda fonksiyonel Manyetik Rezonans Görüntüleme (MRG) çalışması bulunmamaktadır. Çalışmamızda periferik sinir (siyatik sinir) hasarı yapılan sıçanların somatosensoriyel kortekslerindeki değişimler fonksiyonel MRG ile görüntülendi. Bunun için benzer ağırlığa ve büyüklüğe sahip beş adet erkek sıçana sağ, diğer beş erkek sıçana sol taraf sinir hasarı verildi. Sıçanlar aynı klinik ortamlarda, ayrı kafeslerde takip edildi. Anestezi altında aynı Ģiddette elektriksel uyarım verilen sıçanlar fonksiyonel MRG ile aynı protokol altında görüntülendi. Çalışmamızda on sıçanın tümünde cerrahi işlem öncesi var olan somatosensoriyel aktifleşme, post-op 2. günde 9, post-op 15. günde 2 sıçana düĢtü. Post-op 30. günde ise hiç bir sıçandan uyaran alınamadı. Sonuç olarak, periferik sinir hasarı sonrası, duysal geri-bildirim azalmasına bağlı olarak merkezi sinir sistemindeki metabolik aktivitede azalma meydana gelmektedir. Bu çalışmanın bir sonraki aşamasında, periferik sinir hasarının onarımı sonrasındaki merkezi sinir sistemindeki olası değişiklerin fonksiyonel olarak görüntülenmesi, ileriki yıllarda periferik sinir tedavisinde zamanlama konusunda yardımcı olabilir. Anahtar Sözcükler: Periferik sinir hasarı, fonksiyonel manyetik rezonans görüntüleme, somatosensoriyel korteks, merkezi sinir sistemi
Peripheral nervous system is responsible for mediating autonomic functions, conducting sensorial input from environment to the central nervous system, and relaying motor-response from there to muscles and joints. Peripheral nerve injury has a high morbidity ratio in daily life. Injury in both macro- and micro-nerve environment is very important for treatment plan. In micro-level, there are 3 types of injury. In neuropraxia, there is only functional loss. After a couple of weeks, nerve gets its old function, fully. In axonotmesis, axon is ruptured but the connective tissue, surrounding the nerve, is intact. In heavily injured nerves, surgery can be mandontory. In neurotmesis, all nerve with its sorrounding connective tissue are damaged. Surgery should be employed. In macro-level, the impact of injury shows itself at a later stage. So, by waiting, true injured segment can be detected and surgery can be performed after then. Nerve regeneration is now followed up with electrodiagnostic and imaging techniques. Many electrodiagnostic tests are used for monitoring central nervous system, especially somatosensorial cortex reply to peripheral nerve injury. But functional MRI studies are scanty. In our study, somatosensorial cortex functional status of rats with peripheral nerve (sciatic nerve) injury has been imagened with MRI. For this purpose, 10 similar weighted and sized rats were conducted into our study. All of them were male. Sciatic nerve surgical injury was performed in 5 rats' right hindpaws, in 5 rats' left hindpaws. During the experiment, rats were followed in the same room in different cages. Electrical stimulation under anesthesia was given in the same amplitude and they were monitored under functional MRI with same protocols. All rats' somatosensorial cortex were active before the surgery. Post-op 2nd day, this dropped to 9 rats, post-op 15th day dropped to 2 rats. Finally at post-op 30th day, no activation was present in the presumed area. In conclusion, somatosensorial area metabolic activation decreased due to decreased sensorial inputs because of injured peripheral nerves. On foregoing future experiments, the functional status of somatosensorial cortex should be monitored after surgical repair of the nerve itself. Key words: Peripheral nerve injury, functional magnetic resonance imaging, somatosensorial cortex, central nervous system
Peripheral nervous system is responsible for mediating autonomic functions, conducting sensorial input from environment to the central nervous system, and relaying motor-response from there to muscles and joints. Peripheral nerve injury has a high morbidity ratio in daily life. Injury in both macro- and micro-nerve environment is very important for treatment plan. In micro-level, there are 3 types of injury. In neuropraxia, there is only functional loss. After a couple of weeks, nerve gets its old function, fully. In axonotmesis, axon is ruptured but the connective tissue, surrounding the nerve, is intact. In heavily injured nerves, surgery can be mandontory. In neurotmesis, all nerve with its sorrounding connective tissue are damaged. Surgery should be employed. In macro-level, the impact of injury shows itself at a later stage. So, by waiting, true injured segment can be detected and surgery can be performed after then. Nerve regeneration is now followed up with electrodiagnostic and imaging techniques. Many electrodiagnostic tests are used for monitoring central nervous system, especially somatosensorial cortex reply to peripheral nerve injury. But functional MRI studies are scanty. In our study, somatosensorial cortex functional status of rats with peripheral nerve (sciatic nerve) injury has been imagened with MRI. For this purpose, 10 similar weighted and sized rats were conducted into our study. All of them were male. Sciatic nerve surgical injury was performed in 5 rats' right hindpaws, in 5 rats' left hindpaws. During the experiment, rats were followed in the same room in different cages. Electrical stimulation under anesthesia was given in the same amplitude and they were monitored under functional MRI with same protocols. All rats' somatosensorial cortex were active before the surgery. Post-op 2nd day, this dropped to 9 rats, post-op 15th day dropped to 2 rats. Finally at post-op 30th day, no activation was present in the presumed area. In conclusion, somatosensorial area metabolic activation decreased due to decreased sensorial inputs because of injured peripheral nerves. On foregoing future experiments, the functional status of somatosensorial cortex should be monitored after surgical repair of the nerve itself. Key words: Peripheral nerve injury, functional magnetic resonance imaging, somatosensorial cortex, central nervous system