Wilson's disease (WD) is characterized by impaired hepatic copper secretion and subsequent copper accumulation in many organs predominantly liver and brain, secondary to loss of function mutations in the copper transport protein ATP7B. If the disease is recognized too late or treatment is not adequate, brain copper accumulation leads to progressive neurodegeneration with a variety of clinical symptoms. The nigrostriatal dopaminergic system seems rather vulnerable. Midbrain atrophy, however, has not been recognized as one of the prime features of patients with WD.
Here we report quantification of midbrain diameter in 41 patients with WD. Data were correlated to the severity of neurological symptoms and the integrity of dopaminergic neurons measured via dopamine transporter binding. For control, we measured midbrain diameter in 18 patients with no evidence for brainstem dysfunction and 5 patients with progressive supranuclear palsy (PSP).
Patients with WD had a reduced midbrain diameter (15.5 ± 0.4 mm) compared to controls (18.5 ± 0.2 mm). WD patients without neurological symptoms had midbrain diameter that were not different from controls (18.0 ± 0.3 mm), while patients with neurological symptoms showed midbrain atrophy similar to patients with PSP (14.4 ± 0.3 mm versus 14.1 ± 0.3). There was a strong and significant correlation between midbrain atrophy and the severity of neurological symptoms (r= -0.68, p < 0.001) while midbrain atrophy and dopamine transporter binding correlated significantly but was less pronounced (r=0.46, p < 0.001).
In summary, we were able to show, that midbrain diameter is an easy to perform quantification of neurodegeneration induced by brain copper accumulation and that other structures than substantia nigra dopaminergic neurons seem to contribute to midbrain atrophy in WD.