Clinical Trial: Brain Physiology in Polio Survivors


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Sponsored by:	National Institute of Neurological Disorders and Stroke (NINDS)
Information provided by:	Warren G Magnuson Clinical Center (CC)

This study will test whether post-polio syndrome may be due to unrecognized damage to a part of the brain called the motor cortex. Polio is caused by a virus that damages motor neurons in the spinal cord. Most polio survivors recover their strength, but many develop pain, weakness, and fatigue many decades later. It is not known why some people develop this syndrome and others do not. This study will evaluate the integrity of brain pathways in polio survivors with and without post-polio syndrome and in normal volunteers.

Polio survivors between 40 and 75 years of age with or without post-polio syndrome and healthy normal volunteers between 21 and 75 years of age may be eligible for this study. Patients are screened with a medical history, physical examination, magnetic resonance imaging (MRI) scan of the brain, blood tests, and sensory evoked potentials. The MRI uses a powerful magnet, combined with a computer system and radio waves, to produce detailed pictures of the brain. During the scan, the subject lies on a table in a narrow cylinder containing a magnetic field. Sensory evoked potentials measure the excitability of the brain to sensory stimuli. The measurements are obtained from electrodes placed on the scalp.

- Transcranial magnetic stimulation: This procedure maps brain function. A wire coil is held on the scalp, and a brief electrical current is passed through the coil, creating a magnetic pulse that stimulates the brain. During the stimulation, the subject may be asked to tense certain muscles slightly or perform other simple actions to help position the coil properly. The stimulation may cause a twitch in muscles of the face, arm, or leg, and the subject may hear a click and feel a pulling sensation on the skin under the coil. TMS will be done before and after exercise in two muscles (see "Exercise testing" below).

Condition
Postpoliomyelitis

OBJECTIVE: Many persons who survive poliomyelitis develop pain, weakness, and fatigue many decades later. It is not known why some persons develop this syndrome and others do not. One possibility is that polio caused subclinical damage to the motor cortex. Autopsies in some polio patients have found damage to the brainstem and motor cortex as well as to spinal motor neurons. Alternatively, polio may have spared the motor cortex, but the cortex reorganized in different ways to compensate for the loss of spinal motor neurons. This study will first assess the integrity of central motor pathways in polio survivors with and without postpolio syndrome. The second goal will be to investigate differences in the intracortical mechanisms for controlling muscles affected and unaffected by polio.

STUDY POPULATION: 60 patients who survived polio in childhood. Only patients with an unequivocal history of polio will be referred to this study. Half of the patients will have the post-polio syndrome. 30 normal volunteers, aged 21-75.

DESIGN: Patients will be screened at the collaborating institution, the Uniformed Services University of the Health Sciences. Motor evoked potentials will be elicited from all four limbs using transcranial magnetic stimulation to assess central motor conduction time and threshold. Intracortical facilitation will be used to assess using paired-pulse magnetic stimulation. Two muscles will be tested in each patient, one affected by polio and one unaffected by polio. In the affected muscle, intracortical facilitation will be assessed again after exercises it until it fatigues.

OUTCOME PARAMETERS: Cortical thresholds and central motor conduction times to all four limbs will be measured in patients and compared to normal subjects. The mean intracortical facilitation at rest will be compared in affected and unaffected muscles in polio patients with and without post-polio syndrome.

INCLUSION CRITERIA:
POLIO PATIENTS:
Complete screening evaluation.
Meet clinical criteria for diagnosis of past polio (see below).
Meet clinical criteria for the diagnosis of PPS (PPS group only) and have new muscle weakness.
Age 18 or older.
CLINICAL CRITERIA FOR PAST POLIO (CONFIRMED):
Clinically compatible signs and symptoms of paralytic poliomyelitis (acute flaccid paralysis of one or more limbs).
Decreased or absent tendon reflexes on the affected limbs.
No persistent sensory or cognitive loss.
No other apparent cause (including laboratory investigation to rule out other causes of similar syndrome).
Neurological deficit present 60 days after onset of initial symptoms.
Associated with isolation of either vaccine or wild poliovirus from a clinical specimen.
CLINICAL CRITERIA FOR POST-POLIO SYNDROME:
History of polio with partial or complete neurological and functional recovery.
Stable function greater than 15 years.
New onset of one or more of the following: fatigue, weakness, atrophy, muscle pain, functional loss.
Exclusion of other explanations for the symptomatology.
Neurological evaluation demonstrating: lower motor neuron dysfunction (confirmed by EMG, imaging studies or muscle biopsy), no sensory loss.
Must have new onset of muscle weakness in one or more limb muscles, as determined by history and clinical examination.
NORMAL VOLUNTEERS:
Healthy adult volunteers ages 40-75 who are willing to participate.
EXCLUSION CRITERIA:
Neurological diseases or conditions, other than polio, that in the judgment of the investigators may account for the symptoms or interfere with the experimental interventions.
Implanted devices, such as pumps, pacemakers, or metal fragments in the skull or eye.