Increased wave P 300 latency in progressive supranuclear palsy

Visual signs and symptoms of progressive supranuclear palsy

Progressive supranuclear palsy is a rare, degenerative brain disorder and the second most common syndrome in which the patient exhibits 'parkinsonism', that is, a variety of symptoms involving problems with movement. General symptoms include difficulties with gait and balance; the patient walking clumsily and often falling backwards. The syndrome can be difficult to diagnose and visual signs and symptoms can help to separate it from closely related movement disorders such as Parkinson's disease, multiple system atrophy, dementia with Lewy bodies and corticobasal degeneration. A combination of the presence of vertical supranuclear gaze palsy, fixation instability, lid retraction, blepharospasm and apraxia of eyelid opening and closing may be useful visual signs in the identification of progressive supranuclear palsy. As primary eye-care practitioners, optometrists should be able to identify the visual problems of patients with this disorder and be expected to work with patients and their carers to manage their visual welfare.

Prolonged P3 latency and decreased brain perfusion in cerebellar degeneration

OBJECTIVES

To clarify the underlying mechanism of cognitive impairments in patients with cerebellar degeneration using event-related potentials (ERPs) and regional brain perfusion measurement.

MATERIALS AND METHODS

The P3 latency of ERPs was measured during a visual discrimination task in 15 patients with idiopathic late-onset cerebellar ataxia (ILOCA) and 10 age-matched control subjects. Regional brain perfusion was measured by single photon emission computed tomography using N-isopropyl-p[123I] iodoamphetamine.

RESULTS

The mean P3 latency was longer in the patients than in controls. The patients showed lower perfusion in the frontal cortex and in the cerebellum than control subjects. There was a significant correlation between perfusion of the frontal cortex and cerebellum.

CONCLUSIONS

The results indicate that patients with ILOCA exhibit slowing of cognitive information processing and suggest that its cognitive slowing may be due to a disruption of neural circuits between the cerebellum and the frontal cortex.

Electrophysiological comparison between corticobasal degeneration and progressive supranuclear palsy

Multimodal evoked potentials were recorded in four patients with corticobasal degeneration (CBD), four patients with progressive supranuclear palsy (PSP) and 15 normal control subjects. CBD and PSP patients showed significant prolongation of the N200 and P300 latencies of auditory event-related potentials compared with controls. Patients with CBD showed significant prolongation of interpeak latencies between N13 and N20 of short-latency somatosensory evoked potentials compared with the controls and patients with PSP. The present results show that the two diseases have different electrophysiologic features.

Cholinergic and peptidergic systems in PSP

PSP is associated with a widespread cholinergic deficit likely corresponding to a loss in cholinergic neurons. The cholinergic damage dramatically affects the basal ganglia and specific cell groups of the mesencephalon and pons. This provides an anatomically defined basis for motor and supranuclear oculomotor syndromes characteristic of PSP. Unlike Alzheimer's disease and Parkinson's disease with dementia, the disease is not associated with a marked cholinergic deficiency in the cerebral cortex. Various peptides are present at normal concentrations in extrapyramidal and limbic subcortical areas in brains of patients with PSP. Of particular interest, is somatostatin, the levels of which are subnormal in cerebral cortex of patients with dementia of Alzheimer' or Parkinson's disease type.

Topographic mapping of long latency "cognitive" event-related potentials (P 300): a double-blind, placebo-controlled study with amantadine in mild dementia

Amantadine is generally used in the prophylaxis of infection with influenza A, in the treatment of Parkinson's disease and in the treatment of neuroleptic side effects. In this study acute effects of amantadine infusions on event-related potentials (ERP) were studied in 20 mildly demented patients diagnosed according to DSM-III-R criteria. Each patient was treated, in randomized order, with 0.2 g amantadine-sulfate in 500 ml NaCl and 500 ml NaCl placebo, i.v. over one hour with an interval of two weeks in-between. ERPs were investigated in an auditory odd-ball paradigm before as well as 5 hours after the infusion. In addition to 17 EEG records, vertical and horizontal EOGs were recorded. After EOG-minimization and visual artifact rejection the peak latencies of the spatial average were determined by an automatic procedure. There was no effect of amantadine on ERP latencies. N1 of the non-target showed a trend towards amplitude augmentation, P2 amplitude was reduced. As compared to placebo, P300 amplitude of targets was significantly augmented by 3.1 microV (30% of pre-treatment value), confirming the hypothesis that amantadine may influence the P 300 amplitude in the sense of an improved availability of cognitive processing resources.

[Cognitive evoked potentials and HIV infection]

Endogenous event-related potentials (and especially the P300 component) have delayed latencies relative to normal controls in patients with dementias of diverse aetiologies. Moreover, the subcortical varieties of dementia tend to affect also the early-stage N1 and P2 components whereas both types of dementias affect the later-stage N2 and P3 components. However it has become obvious that patients with HIV infection are susceptible to develop progressive, AIDS-related dementia, renamed 'HIV encephalopathy' by the Center for Disease Control. Several studies have shown that endogenous, but also early, components of long latency auditory evoked potentials are prolonged in latency in HIV-demented patients. However, these changes may also be present in class II and III patients and may permit the early recognition of HIV encephalopathy.

Delayed P3 event-related potentials (ERPs) in thalamic hemorrhage

Delayed P3 ERPs were recorded with an acoustic oddball paradigm in 5 patients affected by unilateral thalamic hemorrhage. P3 latencies in these 5 patients were above the normal mean latency of age-matched controls +2/+3 S.D.s. The P3 delay was persistent in serial follow-ups at 6 months from stroke. Normal P3 latencies were instead recorded in 4 patients with paramedian hemorrhage not involving or only partially involving the thalamus.

Mapping of event-related potentials to auditory and visual odd-ball paradigms

This paper reports the results of recordings and maps of event-related potentials (ERPs) obtained in normal subjects, patients with Alzheimer's disease (AD), progressive supranuclear palsy, confusional states, and in subjects with homonymous hemianopsia. ERPs were recorded from 19 scalp electrode derivations using both visual and acoustic paradigms. In normal subjects, the topographical distribution of all ERP components is described in detail. In 45% of AD patients, ERPs were normal; in 35%, although present, ERP components were delayed, while in the other 20% the N2 and P3 peaks could not be recorded. In patients with progressive supranuclear palsy, the normal ERP sequence was not identified. Our findings in normals and in hemianopic patients suggest that the early modulation of stimulus-related potentials could be located in primary associative areas, and that N2, P3a, P3b, SW should have different origins.