Reduziertes Durstempfinden bei der Progressiven Supranukleären Blickparese: Entwicklung eines neuen Bedside-Tests zur Differentialdiagnose von Parkinson Syndromen

Progressive supranuclear palsy (PSP) is a rapidly progressing neurodegenerative disorder belonging to the family of tauopathies and mostly occurring after the 40th decade. The clinical picture is characterized by an akinetic-rigid syndrome and patients often suffer of early postural instability with frequent falls, particularly backward. The namegiving symptom of supranuclear palsy of vertical gaze often occurs late or never at all. Other smptoms like bradykinesia, rigor or frontal signs are less specific and can also occur in other neurodegenerative disorders. Until today there are no biomarkers or diagnostic investigastions that can be used to diagnose PSP definitely antemortem, particularly not at early stages of the disease. Therefore PSP patients are often diagnosed very late in their disease course, or even remain undiagnosed or misdiagnosed throughout their lifetime. Our department performed a questionnaire-study with non-demented, non-depressed patients with clinically probable PSP and age- and stage-matched patients with multiple system atrophy with parkinsonism (MSA-P) and Parkinson’s disease (IPS) as well as healthy controls (K) (N=15 per group). In this survey 73% of the PSP patients reported a decreased sensation of thirst (K=0; MSA-P=7%; IPS=7%; p<0.0001). Those preliminary studies led us to investigate thirst as a parameter of possible differential diagnostic value for PSP. To provoke thirst in a standardized manner, we infused 0.51 M NaCl i.v. for a 50 min. period in age-, gender- and stage-matched PSP, MSA-P and IPS patients (N=10 each) of an independent cohort. They noted in defined intervals for 95 min. their sensation of thirst on a visual analogue scale (0-10). Plasma osmolality was determined at the beginning and end of the infusion and when they reported the first sensation of thirst. The relative increase in osmolality from baseline to the first sensation of thirst was significantly higher in PSP patients compared to MSA-P and IPS. The latency to the first sensation of thirst was significantly longer. PSP patients reported significantly lower thirst than MSA-P and IPS patients for all time points from 20 to 95 min. The maximal thirst score in PSP was significantly lower than in MSA-P and IPS. The thirst score at 25 min. discriminated PSP patients well from MSA-P and IPS. After the test PSP patients drank significantly less to satiation than MSA-P and IPS patients. In summary, we report that hypodipsia occurs frequently and early in PSP, but rarely in IPS and MSA-P. Thirst testing could be helpful in the differential diagnosis of PSP.