OBJECTIVETo investigate the pathology of palatopharyngeal muscle obtained from patients with obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODSThe samples from both groups were studied under HE, nicotinamide adenine dinucleotide-tetrazolium reductase (NADH- TR), modified Gomori trichrome (MGT) and adenosine triphosphatase (ATPase) staining. There were 36 cases of OSAHS who received uvulopalatopharyngoplasty in the experimental group (including 6 mild, 6 moderate and 24 severe cases). There were 6 patients with chronic tonsillitis but without OSAHS as matched control group. Both groups were diagnosed by PSG.

RESULTSCentralized located nuclei and obvious variability of the size of fiber types were observed in both groups. The occurrence rate of the former were 1/6 in control group and 52.8% (19/36) in OSAHS, while the rate of the latter were 4/6 and 58.3% (21/36)respectively. A large number of fibers in both groups (control group 5/6, OSAHS group 28/36) presented an irregularly distributed staining for oxidative activity reaction in NADH stain.Endomysium connective tissue proliferation, a lobular or motheaten appearance, target-like fibers, ragged red fiber (RRF) and muscle necrosis were only observed in OSAHS group.While it was more common in serious OSAHS patients. Dominance of type 1 fibers were observed in matched control group in ATPase stain. Clusters of type 2 fibers or clusters of both type fibers were observed in OSAHS, especially more common in serious OSAHS. There was a predominance of the type 2 fibers in some OSAHS patients.

CONCLUSIONSThe observation of HE and special muscular stain identified that palatopharyngeal muscle of OSAHS patients had pathological lesion. The pathological changes included muscular lesion and abnormal distribution of different fiber types, the rate of type 1 fiber which maintained the opening of upper air way decreased.