Progressive supranuclear palsy: postmortem chemical analysis

Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) was first recognized as a distinct morbid entity by Richardson, Steele and Olszewski a quarter century ago. Subsequent experience has confirmed and extended their original observations. PSP has become familiar as a chronic progressive disorder with extrapyramidal rigidity, bradykinesia, gait impairment, bulbar palsy, dementia and a characteristic supranuclear ophthalmoplegia. It is an important cause of parkinsonism. Its etiology remains obscure. Familial concentrations have not been observed.

Some cases exhibit no oculomotor dysfunction. Dementia is usually mild. Recent neuropsychological studies have defined features consistent with frontal lobe cortical dysfunction. Seizures and paroxysmal EEG activity may occur.

CT and MRI scans show midbrain atrophy early and later atrophy of the pontine and midbrain tegmentum and the frontal and temporal lobes. PET scans have shown frontal hypometabolism and loss of striatal D-2 dopamine receptors. Postmortem studies have documented involvment of both dopaminergic and cholinergic systems. Treatment remains palliative and unsatisfactory.

Levodopa-induced dyskinesia in an autopsy-proven case of progressive supranuclear palsy

It is common for patients with idiopathic Parkinson's disease to develop levodopa-induced dyskinesia. This report provides what we believe is the first videotape presentation of levodopa-induced dyskinesia in a patient with progressive supranuclear palsy. To our knowledge, there is only one previous report of an autopsy-proven case of this kind.

Tremor in Parkinson's disease

Rest tremor is a common feature of Parkinson's disease, but its underlying pathophysiology remains unknown. This review hypothesizes that tremor is related to selective loss of components of the substantia nigra. The relative scarcity of tremor in related Parkinsonian conditions may indicate a dissociation associated with different pathological involvement of the substantia nigra and its connections. Connections of the subthalamic nucleus with the pallidum, modified by cortical and nigral inputs, allow for the transfer of tremorogenic activity to the thalamus. Thalamo-cortical interactions, tempered by cerebellar input, generate the final common pathway for tremor production.

Randomized placebo-controlled trial of donepezil in patients with progressive supranuclear palsy

OBJECTIVE

There is no effective treatment for progressive supranuclear palsy (PSP). Because results of immunochemical and pharmacologic studies suggest that the cholinergic system may play a role in the cognitive and motor features of PSP, the authors investigated the effects of donepezil (10 mg/day), an acetylcholinesterase inhibitor, in 21 patients with PSP (mean age +/- SD; 65.7 +/- 4.7 years) by a randomized, double-blind, placebo-controlled crossover trial.

METHODS

Donepezil and placebo were administered for 6 weeks each with a 1-month washout period. Patients were evaluated before and at the end of each treatment phase. Outcome measures evaluated neuropsychiatric, global cognitive, frontal, memory, motor, and activities of daily living (ADL) status.

RESULTS

Two patients withdrew during the washout phase because of unrelated medical problems. Donepezil-induced systemic side effects were transient and generally mild. Because of worsening of motor function, three patients received 5 mg/day of donepezil. All patients achieved blood and CSF therapeutic levels of donepezil. While the patients were taking donepezil, their Double Memory Test scores improved, whereas their ADL/mobility scores significantly worsened.

CONCLUSION

The findings suggest that acetylcholinesterase inhibitors such as donepezil have at best selective, modest effects on cognition in patients with PSP. In light of its deleterious effects on ADL/mobility, donepezil is not recommended for this patient population.

Pharmacological evaluation of the cholinergic system in progressive supranuclear palsy

Severe cholinergic loss occurs in the brains of patients with progressive supranuclear palsy. To evaluate the functional implications of this neuronal deficit, dose-response curves were obtained in patients with progressive supranuclear palsy and normal control subjects undergoing intravenous cholinergic blockade (scopolamine) and stimulation (physostigmine). Physostigmine had no significant neurobehavioral effects at any dose in patients with progressive supranuclear palsy. Scopolamine, at low and medium doses, significantly impaired memory performance of both groups, but worsened the gait of only the patients. High-dose scopolamine, which could not be tolerated by the patients, resulted in gait deterioration among control subjects. Thus, patients with progressive supranuclear palsy have increased sensitivity to cholinergic blockade compared to control subjects. Since loss of cholinergic neurons appears to contribute to the pathogenesis of certain cognitive and motor deficits found in progressive supranuclear palsy, the use of oral anticholinergics should ordinarily be avoided in this disorder. On the other hand, physostigmine at clinically tolerated dose levels seems to be therapeutically ineffective.

Cerebrospinal fluid acetylcholinesterase in progressive supranuclear palsy: reduced activity relative to normal subjects and lack of inhibition by oral physostigmine

Acetylcholinesterase (AChE) activity was measured in lumbar cerebrospinal fluid (CSF) of 11 patients with progressive supranuclear palsy (PSP) and 18 age-matched healthy control subjects. Mean CSF AChE activity in PSP subjects was significantly reduced by 31% relative to control subjects (p less than 0.002). In the light of evidence of a central cholinergic deficit, physostigmine was administered orally (0.5-2.0 mg every two hours, six times a day for 10 days) to eight of the 11 PSP patients. CSF was sampled when the patients were on placebo and when receiving physostigmine and CSF AChE and butyrylcholinesterase (BChE) activities were measured. There was no significant change in either CSF AChE or BChE activities following physostigmine treatment. These data suggest that the doses of physostigmine used were insufficient to produce marked inhibition of AChE within the central nervous system.