Walter Widdig

Neuropsychological investigations and event-related potentials in obstructive sleep apnea syndrome before and during CPAP-therapy

Patients with obstructive sleep apnea syndrome (OSAS) suffer from daytime sleepiness and a decline of cognitive functions. The study evaluated whether special cognitive disabilities predominate in OSAS. Besides the number connection test (ZVT), judging information processing and working velocity, computer-assisted (Wiener Testsystem and Zimmermann Testbatterie) neuropsychological testing was performed in 31 OSAS patients (50.1 +/- 9.4 years) before starting nasal continuous positive airway pressure (nCPAP) therapy. Identical test battery was performed in 10 male healthy volunteers (48 +/- 9.9 years). In addition visual evoked event-related potentials (ERPs) were recorded, the P3-component was evaluated. Impairment of alertness (P < 0.001), selective attention (P < 0.001) and continuous attention (P < 0.001) could be revealed, vigilance was not altered. Cognitive deficits were correlated with the degree of nocturnal hypoxemia. They were not linked to the apnea/hypopnea-index (AHI), arousal index or vigilance parameters. During 6 months of nCPAP-therapy (15 patients) alertness and continuous attention improved significantly (P < 0.01), intra-individual different pathological results persisted however. P3 latencies also remained prolonged. Chronic intermittent nocturnal hypoxemia in OSAS-patients obviously leads to cognitive deficits. ERP partially generated in subcortical cerebral structures represent a neurophysiological tool indicating brain dysfunction which cannot be evaluated by neuropsychological tests. Objective neuropsychological testing is needed in revealing therapeutic effects in OSAS-patients. Remaining deficits during sufficient nCPAP-therapy may reflect irreversible hypoxic cerebral damage.

Functional magnetic resonance imaging mirrors recovery of visual perception after repetitive tachistoscopic stimulation in patients with partial cortical blindness

We investigated three patients with partial cortical blindness after brain injury by means of functional magnetic resonance imaging (fMRI) before and after the application of a daily visual stimulation-therapy over a period of 6 months. Before therapy, fMRI data showed a severely reduced blood-oxygen-level-dependent (BOLD) signal in primary visual cortex when compared to healthy volunteers. Following several months of rehabilitative therapy a neuropsychological improvement of visual functions was accompanied by an increase in BOLD signal of residual perilesional regions whereas fMRI data of the control group remained unchanged. A high capacity of functional recovery and synaptic plasticity of surviving perilesional neuronal structures of primary visual cortex followed by an increased input into post-connected visual areas can be discussed as a basis for the reoccurrence of visual functions.

Comparison of driving simulator performance and neuropsychological testing in Narcolepsy

Daytime sleepiness and cataplexy can increase automobile accident rates in narcolepsy. Several countries have produced guidelines for issuing a driving license. The aim of the study was to compare driving simulator performance and neuropsychological test results in narcolepsy in order to evaluate their predictive value regarding driving ability. Thirteen patients with narcolepsy (age: 41.5+/-12.9 years) and 10 healthy control patients (age: 55.1+/-7.8 years) were investigated. By computer-assisted neuropsychological testing, vigilance, alertness and divided attention were assessed. In a driving simulator patients and controls had to drive on a highway for 60 min (mean speed of 100 km/h). Different weather and daytime conditions and obstacles were presented. Epworth Sleepiness Scale-Scores were significantly raised (narcolepsy patients: 16.7+/-5.1, controls: 6.6+/-3.6, P < or = 0.001). The accident rate of the control patients increased (3.2+/-1.8 versus 1.3+/-1.5, P < or = 0.01). Significant differences in concentration lapses (e.g. tracking errors and deviation from speed limit) could not be revealed (9.8+/-3.5 versus 7.1+/-3.2, pns). Follow-up investigation in five patients after an optimising therapy could demonstrate the decrease in accidents due to concentration lapses (P < or = 0.05). Neuropsychological testing (expressed as percentage compared to a standardised control population) revealed deficits in alertness (32.3+/-28.6). Mean percentage scores of divided attention (56.9+/-25.4) and vigilance (58.7+/-26.8) were in a normal range. There was, however, a high inter-individual difference. There was no correlation between driving performance and neuropsychological test results or ESS Score. Neuropsychological test results did not significantly change in the follow-up. The difficulties encountered by the narcolepsy patient in remaining alert may account for sleep-related motor vehicle accidents. Driving simulator investigations are closely related to real traffic situations than isolated neuropsychological tests. At the present time the driving simulator seems to be a useful instrument judging driving ability especially in cases with ambiguous neuropsychological results.

„Frontalhirnsyndrom” nach Schädel-Hirn-Trauma oder zerebrovaskulären Erkrankungen

ZusammenfassungDer klinisch gebräuchliche Terminus des „Frontalhirnsyndroms” beschreibt eine heterogene Symptomatik, welche nicht nur nach Schädigung des präfrontalen Kortex, sondern auch bei Läsionen von tieferliegenden, mit dem präfrontalen Kortex in Verbindung stehenden Strukturen beobachtet werden kann. Nach den im Vordergrund stehenden klinischen Merkmalen und unter Berücksichtigung der dabei geschädigten anatomischen Strukturen können Schädigungen des präfrontalen Kortex in 3 Untergruppen unterteilt werden: 1. das desorganisierte Syndrom, welchem eine Schädigung der dorsolateralen Konvexität und ihrer Verbindungen zugrunde liegt; 2. das enthemmte Syndrom, welches durch Läsionen des orbitofrontalen Kortex und seiner Verbindungen verursacht wird und 3. das apathische Syndrom infolge mittelliniennaher Läsionen mit Schädigung der Verbindungen zwischen Gyrus cinguli und supplementär-motorischem Areal. Da intrazerebrale Läsionen nur selten auf die beschriebenen Regionen beschränkt sind finden sich häufig Mischbilder mit bisweilen bizzarren psychopathologischen Auffälligkeiten. Anhand von 4 Fallbeispielen von Patienten mit Schädel-Hirn-Trauma (n=2) oder zerebrovaskulärer Erkrankung (n=2) werden die klinische Problematik veranschaulicht und diagnostische sowie therapeutische Maßnahmen besprochen.SummaryThe term „frontal lobe syndrome” comprises a variety of different clinical syndromes produced by focal lesions involving the prefrontal cortex. However, similar syndromes can be observed after lesions involving subcortical structures connected with the prefrontal cortex in neuronal networks. With respect to the different clinical pictures and underlying brain lesions, prefrontal lobe dysfunction may be divided into a disorganized type, caused by lesion of the dorsolateral prefrontal lobe and its connections, a disinhibited type that can be observed following lesions of the orbitofrontal cortex, and an apathetic type following lesions affecting the functional balance between the cingulum and the supplementary motor area. As intracerebral lesions are rarely limited to the brain regions described, in the majority of patients various degrees of behavioural dysfunction can be observed. The case reports of four patients illustrating the three major prefrontal syndroms following severe head injury (n=2) or cerebrovascular disease (n=2) are presented and diagnostic implications as well as possible treatment strategies are discussed.