Chiari type 1 anomaly in pseudohypoparathyroidism type Ia: pathogenetic hypothesis

Abstract

This study aims to report a patient with Chiari type 1 malformation (CM1) occurring in the context of pseudohypoparathyroidism type 1a (PHP-Ia) that we believe represents the first instance of this association in the current literature. The authors describe the case of a 6-year-old girl diagnosed with PHP-Ia who presented an associated tonsillar descent. During the follow-up, the skull vault and the occipital squama became extremely thickened at the same time as the tonsillar herniation showed a marked regression. Chronic tonsillar descent has been reported in diverse genetic and metabolic diseases of bone. A constant finding in PH-Ia consists of changes that mainly involve the bones of the patients' hands and feet. Cerebral anomalies have also been documented in PHP-Ia, especially cerebral calcifications, but in contrast involvement of the skull bones has seldom been described in this condition. The authors briefly discuss the probable role played by the observed skull changes in the origin and subsequent regression of the tonsillar descent in this child. We suggest that CM1 may develop in patients with PHP-Ia and that it should be actively sought, especially in individuals diagnosed with PHP-Ia presenting with neurological manifestations. Probably, the seeming rarity of chronic tonsillar descent in PHP-Ia is due to the fact that many patients with this condition are rarely investigated with magnetic resonance.