Nucleus of the tractus solitarius metastasis: Relationship to respiratory arrest?

Background: A 52-year-old woman with metastases in brain and bone had clini cal and radiological. response to therapy but died about 10 weeks after dia gnosis. General autopsy failed to identify a primary neoplasm or an anatomi c cause of death. Investigation of sudden respiratory cessation was a consi deration when undertaking an anatomic study of the brain. Methods: Review o f patient records and careful examination of the brain following autopsy we re carried out. Results: The patient had terminal episodes of hypersomnia b ut episodes of sleep apnea were not observed, She received no respiratory s upport and no respiratory difficulties were recorded until she was pronounc ed dead at 7 a.m. Autopsy revealed metastatic adenocarcinoma in a pattern s uggestive of a primary pulmonary neoplasm, including multiple cerebral meta stases, although no significant pulmonary lesions of any type were found. A 0.2 cm metastatic adenocarcinoma was found in the nucleus of the tractus s olitarius (NTS), No other tumor was present in the brain stem. Conclusions: Unilateral destruction of the NTS in the medulla would have severely distu rbed the most critical point of convergence of autonomic and voluntary resp iratory control and of cardiocirculatory reflexes in the central autonomic network. It is postulated that this caused respiratory arrest during a stat e transition from sleeping to waking. Few metastases to the medulla are rep orted, most are relatively large, and several have caused respiratory sympt oms before death. The very small metastasis in our patient could be the dir ect anatomic cause of death, and as such it is an unusual complication of m etastatic disease of which clinicians should be aware. It is speculated tha t dysfunction of direct NTS connections to the pens or of connections passi ng close to the metastatic deposit resulted in terminal hypersomnia.