Pontomesencephalic Atrophy and Postural Instability in Wilson Disease

BACKGROUND AND PURPOSE: The MR Parkinsonism index helps in differentiating progressive supranuclear palsy from Parkinson disease and multisystem atrophy. Pontomesencephalic involvement is common in neurologic Wilson disease, but there is no prior study evaluating the MR Parkinsonism index and its indices in Wilson disease. We report the MR Parkinsonism index and its indices in Wilson disease and correlate these changes with clinical severity and postural reflex.

MATERIALS AND METHODS: Thirteen individuals with neurologic Wilson disease were included, and their clinical details, including neurologic severity, postural reflex abnormality, and location of signal changes on MR imaging, were noted. The 3D BRAVO T1 sequence was used for measurement of the MR Parkinsonism index and its indices. The MR Parkinsonism index and its indices were also obtained in 6 age- and sex-matched controls. The morphometric parameters in Wilson disease were compared with those in with healthy controls and among the patients with and without abnormal postural reflex.

RESULTS: The midbrain area was reduced in patients with Wilson disease compared with controls (112.08 ± 27.94 versus 171.95 ± 23.66 mm², P = .002). The patients with an abnormal postural reflex had an increased MR Parkinsonism index and pons-to-midbrain ratio compared with controls, whereas these parameters were equivalent in patients with normal postural reflex and controls. The patients with abnormal postural reflex had more severe illness, evidenced by higher Burke-Fahn-Marsden scores (51.0 ± 32.27 versus 13.75 ± 12.37, P = .04) and neurologic severity grades (2.57 ± 0.53 versus 1.67 ± 0.82, P = .04).

CONCLUSIONS: An increase in the MR Parkinsonism index in Wilson disease is mainly due to midbrain atrophy and it correlates with neurologic severity and abnormal postural reflex.