Thickness and histologic and histochemical properties of the superior pharyngeal constrictor muscle in velocardiofacial syndrome

Abstract

Background: Velocardiofacial syndrome (VCFS) is one of the most common multiple anomaly syndromes in humans. Pharyngeal hypotonia, one of the most common findings in VCFS, contributes to hypernasal speech, which occurs in approximately 75% of individuals with VCFS.

Objective: To evaluate the thickness and histologic and histochemical properties of the superior pharyngeal constrictor (SPC) muscle in patients with VCFS to determine whether a muscle abnormality exists that might contribute to the hypotonia seen in these patients. Subjects The SPC muscle thickness in 26 VCFS patients (18 male and 8 female; age range, 3-29 years) was compared with SPC muscle thickness in age- and sex-matched controls using magnetic resonance images. The histologic and histochemical properties of the SPC muscle in 9 VCFS patients (6 male and 3 female; age range, 4-12 years) were compared with SPC muscle in 3 adult cadavers without VCFS (all male; age range, 80-86 years) using specimens obtained during pharyngeal flap surgery.

Results: The thickness of the SPC muscle was significantly less in patients with VCFS (2.03 mm) than in patients without VCFS (2.85 mm). The SPC muscle contained a significantly greater proportion of type 1 fibers in patients with VCFS (27.7%) than in adults without VCFS (17.9%), and the diameter of the type 1 fibers was significantly smaller in patients with VCFS (21.6 micro m) than in adults without VCFS (26.6 micro m).

Conclusions: Differences in the thickness and histologic and histochemical properties of the SPC muscle found in patients with VCFS compared with individuals without VCFS may offer insight into the cause of pharyngeal hypotonia and hypernasal speech seen in these patients.