The localization of central pattern generators for swallowing in humans--a clinical-anatomical study on patients with unilateral paresis of the vagal nerve, Avellis' syndrome, Wallenberg's syndrome, posterior fossa tumours and cerebellar hemorrhage.

BACKGROUND

Our understanding of brainstem swallowing centers is mainly based on experimental animals. In order to solve this problem also in humans, a clinical-anatomical study on dysphagic patients with different lesion patterns was performed.

METHODS

We studied 43 consecutively admitted dysphagic patients with unilateral paresis of the vagal nerve (PVN), Avellis' syndrome (AS), Wallenberg's syndrome (WS), posterior fossa tumour (PFT) or cerebellar hemorrhage (CH) with regard to clinical and anatomical aspects.

RESULTS

There was a continuum with regard to functional outcome from neurogenic dysphagia (ND): Patients with PFT or CH had a significantly worse outcome than patients with WS; the outcome of WS patients was significantly worse than that of patients with PVN or AS. In AS only the Nucleus ambiguus (NA) and its surrounding reticular formation (RF) were affected. In all patients with WS, the infarctions of the dorsolateral medulla were situated in the rostral third of the medulla and affected the NA and the Nucleus tractus solitarii (NTS) with their surrounding RF. In patients with PFT and CH, the NTS and its surrounding RF were affected on both sides. The overlap area of WS and PFT lesions is situated in the NTS and the surrounding RF, especially in its Nucleus parvocellularis.

CONCLUSIONS

Our results point to the fact, that in humans the dorsomedial central pattern generators (CPGs) for swallowing are situated in the rostral part of the dorsal medulla oblongata near the NTS/surrounding RF (especially Nucleus parvocellularis) and that the dorsomedial CPGs are superior to the ventrolateral CPGs (near the NA/surrounding RF) with regard to their swallowing-relevance. Furthermore, we hypothesize that due to the individual asymmetry of the swallowing-dominant forebrain hemisphere - the outcome from ND in WS depends on the side of the medullary infarction.