Cognitive impairment as a central cholinergic deficit in patients with Myasthenia Gravis.

BACKGROUND: The purpose of this study was to investigate with neurophysiological and neuropsychological methods such as pupillometry, cognitive test and Hamilton Depression Rating Scale (HAM-D) the hypothesis of Central Nervous System (CNS) cholinergic involvement in patients with Myasthenia Gravis (MG). METHODS: Thirty-two patients (32) with MG and a mean age of 51.1 ± 17.2 volunteered to participate in this investigation, while thirty-three (33) healthy subjects with a mean age of 50.2 ± 14.8 served as controls. All subjects underwent pupillometric measurements and performed the Wechsler Memory Scale (WMS) and HAM-D. The pupillometric indices studied were: 1) latency for the onset of constriction (T1), 2) maximum constriction velocity (VCmax) and 3) maximum constriction acceleration (ACmax). RESULTS: T1 was found significantly increased by 21.7% (p < 0.05) in MG patients as compared to healthy subjects. Conversely, VCmax and ACmax were significantly decreased in MG patients by 33.3% (p < 0.05) and 43.5% (p < 0.05) respectively, as opposed to healthy subjects. Additionally, MG patients showed significantly decreased score in WMS by 41.6% (p < 0.05) as compared to healthy controls. No significant difference was found for HAM-D between the two groups. CONCLUSIONS: VCmax and ACmax are governed mainly by the action of the Parasympathetic Nervous System, through acetylcholine. The results of this study demonstrate that the CNS may be affected in MG and support the hypothesis that MG has central cholinergic effects manifested by cognitive dysfunction.

Pupil reaction to light in Alzheimer's disease: evaluation of pupil size changes and mobility.

AIMS: The aim of the study is to assess pupil size changes and mobility evaluation as a diagnostic marker in patients with probable Alzheimer's disease (AD). MATERIAL AND METHODS: Twenty-three control subjects and 23 patients with probable AD entered the study. The latter patients had been under observation for 2 years and had undergone all necessary examinations to verify their initial diagnosis. A full record of the pupil's reaction to light was registered. Ten parameters from these data were measured, reported and then compared in both group of subjects. RESULTS: Patients with probable AD had abnormal pupillary function compared with such function in healthy aging. All pupillary light reflex (PLR) variables differed significantly between the two groups (p<0.005) except baseline pupil diameter (D1) and minimum pupil diameter (D2). Maximum constriction acceleration (ACmax) was the best predictor in classifying a subject as normal or as AD with perfect classification ability (area under the curve =1, p<0.001). In addition, the correlation between the percentage recovery-redilatation (%D1) and ACmax was highly negative in the group of AD patients (r = -0.808, p<0.005). CONCLUSIONS: Pupil size changes and mobility examination may be a fast, non-invasive and efficient additional diagnostic marker in AD diagnosis.