title: The role of ischemic neurodegeneration of the nodose ganglia on cardiac arrest after subarachnoid hemorrhage: an experimental study.
abstract: BACKGROUND
  The heart is innervated by several systems that contribute to the control of the heart's rhythm. The cardiac fibers of the vagus nerve have an important role in the regulation of heart rhythm under many emotional and physical conditions. Severe electrocardiographic disturbances have been reported following subarachnoid hemorrhage (SAH), but ischemic neuronal degeneration of the nodose ganglion of the vagus nerve has not been previously investigated. We examined if there is a relationship between ischemic injury of the nodose ganglion of the vagus nerve and the severity of heart rhythm disorders after subarachnoid hemorrhage.
  
  
  METHODS
  This study was conducted on 20 rabbits. Four rabbits were used as a baseline group. Experimental subarachnoid hemorrhage was applied to half of the remaining animals (n = 8) by injecting homologous blood into the cisterna magna, and the others (SHAM group, n = 8) were injected with isotonic saline solution in the same manner. For 20 days after the injection, heart rhythm changes were observed daily. After the experiment, normal and ischemic neuron densities in the nodose ganglia of the vagus nerves were examined stereologically. The number of heart rhythm irregularities and the number of degenerated neurons in the nodose ganglia were compared statistically.
  
  
  RESULTS
  The normal heart rhythm rate was 280 ± 45/min. At the beginning of the SAH, the average heart rate was 220 ± 30/min; about 10 hours later, it decreased to 189 ± 30/min, indicating severe bradycardia. However, after 7 days, the average heart rate had increased to 350 ± 30/min. Six animals died due to irregularities in cardiac function and respiration. Histopathological examinations showed that the average density of normal neurons in the nodose ganglion was 10,500 ± 2500 in the baseline animals and the SHAM group, but the normal neuron density was 8250 ± 1500 in survivors and 6450 ± 1330 in dead animals. The ischemic neuronal degeneration in the nodose ganglia was more severe in the dead animals than in the survivors (p < 0.0001).
  
  
  CONCLUSIONS
  Afferent vagus nerves originating from the nodose ganglia have an important role in regulating heart rhythm via their afferent fibers and efferent connections. If neurons of the nodose ganglia are lesioned due to ischemic insult during subarachnoid hemorrhage, heart rhythm regulation by vagus afferent reflexes is disturbed. Vagus pathway paralysis may result in indirect sympathetic overactivity. The development of tachycardia causes depletion of the heart's reserves, and cardiac arrest may be inevitable following extensive subarachnoid hemorrhage.
authors.affiliation: Department of Neurosurgery, Ataturk University, Medical Faculty,Erzurum, Turkey. nmda11@hotmail.com
authors.forename: Mehmet D
authors.initials: MD
authors.lastname: Aydin
authors.forename: Ayhan
authors.initials: A
authors.lastname: Kanat
authors.forename: Adem
authors.initials: A
authors.lastname: Yilmaz
authors.forename: Murteza
authors.initials: M
authors.lastname: Cakir
authors.forename: Mucahit
authors.initials: M
authors.lastname: Emet
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Cakir
authors.forename: Sahin
authors.initials: S
authors.lastname: Aslan
authors.forename: Sare
authors.initials: S
authors.lastname: Altas
authors.forename: Cemal
authors.initials: C
authors.lastname: Gundogdu
mesh_terms: D000818:Animals; D001369:Axons / Q000473:pathology; D001933:Brain Stem / Q000473:pathology; D002470:Cell Survival; D003391:Cranial Nerves / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D004562:Electrocardiography / Q000379:methods; D006323:Heart Arrest / Q000209:etiology* / Q000473:pathology*; D006339:Heart Rate / Q000502:physiology; D009410:Nerve Degeneration / Q000209:etiology* / Q000473:pathology; D009474:Neurons / Q000473:pathology*; D009620:Nodose Ganglion / Q000473:pathology*; D011817:Rabbits; D013345:Subarachnoid Hemorrhage / Q000150:complications*; D014630:Vagus Nerve