We present a documented observation showing the existence of a biased representation of verticality in PD, resulting in a severe retropulsion and recurrent falls, and a camptocormia likely compensatory. A specific rehabilitation led to a spectacular result.

A 68-year-old patient with Parkinson's disease fall backward 3 times a day. He presented an important camptocormia. There were no spinal muscular amyotrophy neither spinal canal stenosis on the lumbar tomography. The Postural vertical (PV) was tilted backward at −9° (normal for this age=−1.1°±1.4°). Our interpretation was that retropulsion was due to a backward tilt of the internal model of verticality, which led to recurrent falls. Camptocormia was mainly compensatory.

The patient underwent an intensive rehabilitation program of 15 days including: erectus spinae muscles strengthening, realization of postural exercises thanks to mirror. A modulation of the internal model of verticality was undertaken on the basis of theoretical arguments (synthesis of graviceptive vestibular and somatosensory information) and on experimental studies: 30° forward tilted posture on a tilt table, bodyweight support walking, vibration of tibialis anterior's tendons. PV measurements before and after these technics confirmed the relevance of this approach.

After 2 weeks the results were spectacular (Table 1): posture spontaneously more upright (35mm gain in C7 position), attenuated retropulsion (objectively assessed using the BDS), and normalization of PV=0.1°. At discharge the patient was instructed to daily perform the exercises taught. Reviewed at M2 and M6, he was very satisfied with a dramatic reduction of fall frequency and the feeling to stand better.

This observation brings a new insight about the nature of some postural disorders in PD, and suggests the interest of a novel rehabilitation dedicated to the sense of upright.