A new classification of cerebral palsy based upon neurophysiologic considerations

Laryngeal dystonia in a case of severe motor and intellectual disabilities due to Japanese encephalitis sequelae

Laryngeal dystonia is characterized by stridor due to vocal cord dystonia and is observed in extrapyramidal disorders. Recently, botulinum toxin injection has been used as a primary therapy. Generally, severe motor and intellectual disabilities (SMID) are frequently complicated by various types of respiratory disorders. We report a SMID case with Japanese encephalitis sequelae showing repeated vocal cord abductor disturbance due to laryngeal dystonia, in addition to generalized dystonia, in whom MRI revealed basal ganglia lesions. Tracheostomy was effective for the case, and we believe that botulinum toxin injection may be inappropriate in SMID, both ethically and technically. Also, laryngeal dystonia should be considered as a cause of respiratory disorders in SMID.

Clinical and neuropathological findings in severe athetoid cerebral palsy: a comparative study of globo-Luysian and thalamo-putaminal groups

We divided cases of severe athetoid cerebral palsy originating perinatally into two groups neuropathologically, the "globo-Luysian group" (GL) and the "thalamo-putaminal group" (TP). The major abnormal sites in GL were the pallidum and subthalamic nucleus, and in TP the thalamus and putamen. The lesions in TP were more widespread and frequently accompanied by fibrillary gliosis in the central gray matter of the midbrain, and subthalamic nuclei were dominantly devastated. Concerning the etiology, GL and TP were related to perinatal severe jaundice and neonatal asphyxia, respectively. The patients in TP showed lower mental ability and suffered from more intractable convulsions than those in GL. In GL, rigidospasticity was frequently demonstrated with fluctuation of athetoid movements, while in TP various abnormalities of muscle tone were observed, with rather restricted athetosis.

Control of isometric muscle activity in cerebral palsy

Voluntary control of muscle contraction was examined in five adults with cerebral palsy, who were required to track a moving target by continuously varying the level of isometric contraction of elbow flexor muscles (measured by EMG). First performance varied from minimal control to almost normal control, depending on the severity of disability. Practice over 12 weeks reduced inappropriate muscle activity in the most disabled patients, but there was no increase in appropriate muscle activity for any patient beyond that observed after the first few minutes of tracking. Thus their ability to translate a visual response into the appropriate motor activity was impaired, and there was no evidence of potential to overcome this. This supports the authors' earlier proposal that impairment of sensory-motor learning is the primary cause of functional disability in cerebral palsy. The EMG tracking task may provide a technique for assessing the ability of individuals with cerebral palsy to control muscle contraction.

Motor control deficits of orofacial muscles in cerebral palsy

Voluntary control of the masseter and orbicularis oris superioris muscles was examined in able bodied and cerebral palsied subjects using visual tracking tasks. A smoothed measure of muscle activity (the full-wave rectified and low-pass filtered electromyogram) was presented as a marker on a computer display screen and the subjects could control the vertical position of the marker by voluntarily altering the level of isometric contraction of one of the muscles. A target marker was also displayed on the screen and the subjects were required to follow or "track" the irregular movements of this target with the response marker. Their success in aligning the response marker with the target was analysed for these orofacial muscles. The masseter is influenced by muscle spindle based reflexes, while the orbicularis oris superioris lacks such reflex control. The cerebral palsied subjects displayed similarly poor control over both muscles, implying that their voluntary motor deficits are not related to abnormal muscle spindle based reflexes. It is suggested that the impairment may be related to perceptual-motor integration.

Voluntary control of arm movement in athetotic patients

Visual tracking tests have been employed to provide a quantitative description of voluntary control of arm movement in a group of patients suffering from athetoid cerebral palsy. Voluntary control was impaired in all patients in a characteristic manner. Maximum velocity and acceleration of arm movement were reduced to about 30-50% of their values in normal subjects and the time lag of the response to a visual stimulus was two or three times greater than in normals. Tracking transmission characteristics indicated a degree of underdamping which was not presnet in normal or spastic patients. This underdamping could be responsible for a low frequency (0·3-0·6 Hz) transient oscillation in elbow-angle movements associated with sudden voluntary movement. The maximum frequency at which patients could produce a coherent tracking response was only 50% of that in normal subjects and the relationship between the electromyogram and muscle contraction indicated that the mechanical load on the biceps muscle was abnormal, possibly due to increased stiffness of joint movement caused by involuntary activity in agonist and antagonist muscles acting across the joint.

Measurement of involuntary arm movement in athetotic patients

Visual tracking tests have been used to obtain a quantified statistical description of the involuntary movements of the arm about the elbow joint in a group of patients suffering from athetoid cerebral palsy. Three separate components of involuntary activity can be recognized and it is possible that each may be a different physiological mechanism. First there are irregular movements which are represented by a continuous power spectrum which decreases with increasing frequency, reaching a negligible value between 2-3 Hz. The second component is a rhythmical low frequency movement which is indicated by a predominant peak in the power spectrum at a frequency of 0·3-0·6 Hz. The presence of this peak was predicted in a previous paper because of underdamping demonstrated in the closed loop voluntary control of movement in athetosis. The third component is the athetoid action tremor in which both agonist and antagonist muscle groups contract vigorously but asynchronously at a frequency of 1·5-4 Hz.

Comparison of the tonic stretch reflex in athetotic patients during rest and voluntary activity

An electromyographic technique was used to record the tonic stretch reflex (TSR) responses to passive sinusoidal stretching of biceps brachii muscle in athetotic patients. The TSR transmission characteristics measured while the patient was in a relaxed state were compared with those measured while the patient was voluntarily active. The resting TSR and action TSR were found to differ markedly. Sensitivity, pattern, duration, and timing of the TSR responses were all changed during voluntary activity. The results suggest that the TSR in athetosis is functionally reorganized by supraspinal influences during voluntary activity. It is proposed that athetoid movements and action tremor may be a manifestation of abnormal action TSR caused by faulty supra-spinal control during activity.

Electromyographic study of the rigidospasticity of athetosis

The static and dynamic components of the tonic stretch reflex and shortening reactions have been studied in 10 patients with athetosis. EMG activity could be recorded only from the biceps muscle when the patient was at rest. The dynamic stretch reflex increased with the velocity of stretching in all muscles examined except the biceps. The biceps stretch reflex was found to be inhibited by increasing muscle length, whereas the stretch reflexes of triceps, hamstrings, and quadriceps muscles were facilitated by increasing muscle length. Reinforcement increased resting activity in the biceps and the dynamic shortening reaction of the triceps muscle. Both these effects were suppressed by the action of phenoxybenzamine. Although phenoxybenzamine was shown to reduce muscle tone in a double-blind controlled trial, no corresponding improvement was detected in involuntary movements or the patients' performance in a tracking test. The differences between the pattern of hypertonus in athetosis, Parkinson's disease, spasticity, and activated normal subjects are presented in discussion.