[Axial (neck and trunk) rigidity in Parkinson's disease, striatonigral degeneration and progressive supranuclear palsy].

Our previous study showed that the alternating knee tilt test in supine position is a useful method to assess the trunk rigidity. We investigated the progression of axial (neck and trunk) rigidity in Parkinson's disease (PD), striatonigral degeneration (SND), and progressive supranuclear palsy (PSP) by using this method. We assessed rigidity on a scale of 0 (absent) to 3 (severe) on five parts of the body: neck, trunk, wrist, elbow and knee in 57 patients with PD, 13 patients with SND and 18 patients with PSP. In PD patients, the degree of neck and trunk rigidity correlated well with the duration of disease and the staging scale. There was neck rigidity in 27% of PD patients with unilateral involvement of the limbs, but the trunk tonus was normal in them. There was rigidity in the neck and trunk of all PD patients with bilateral involvement of the limbs. When the limb rigidity was predominant on one side, the trunk rigidity was predominant on the opposite side. In SND patients, the degree of neck and trunk rigidity roughly correlated with the duration of disease and the staging scale. In SND patients with unilateral involvement of the limbs, tonus of the neck and trunk was normal. In SND patients with bilateral involvement of limbs, there was rigidity in both the neck and the trunk. In PSP patients, the degree of neck rigidity correlated well with the duration of disease and the staging scale, but the degree of rigidity in the trunk and limb remained relatively mild even at the advanced stage. Accordingly, in PSP patients there was a dissociation of the degree of neck rigidity from that of trunk and limb rigidity. In conclusion, the assessment of axial (neck and trunk) rigidity may be useful for the clinical diagnosis of parkinsonism and the staging scale scoring.