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Biomedical subjects

R R Young

Publications and source records attributed to R R Young.

At least 55 records · Page 3Linked to original sources
PubMed1987

Physiologic and pharmacologic approaches to spasticity.

The term spasticity is used to describe many relatively unrelated syndromes and, because they share few common pathophysiologic mechanisms, it is not possible to define the physiology or pharmacology of spasticity. In patients with spastic paresis, it is the latter negative symptom (rather than the spasticity) that accounts for almost all the functional disability. Clinical neurophysiologic techniques are useful for categorization of patients with clinically identical syndromes into subgroups which respond to different therapies. Fusimotor or spindle primary afferent hyperactivity have not been demonstrated in spastic patients; reduction in central inhibitory mechanisms probably accounts for spastic hyper-reflexia. Increased passive muscle stiffness may also be clinically significant. Therapies for spasticity include elimination of causative or enhancing factors, frequent muscle stretching, surgical approaches and chemotherapy. The latter includes dantrolene (which weakens muscles), baclofen (particularly useful for reduction of flexor spasms and flexor dystonia in patients with spinal lesions) and diazepam.

Animals↗
PubMed1987

Spasticity.

Spasticity has been defined as velocity-dependent hyperactivity of stretch reflexes; it is therefore only one aspect of the complex syndrome produced by a lesion of the upper motoneuron. Although spasticity may be partially responsible for joint contractures, it does not produce most of the functional disability experienced by patients with upper motoneuron lesions. Paresis, fatigability, lack of dexterity, etc., account for most of these patients' complaints. The pathophysiology of spasticity is poorly understood but appears to be related to an increased excitatory state at the segmental spinal level; there is no evidence for increased sensitivity of muscle spindles in spastic patients. Several mechanisms for this increased excitability within the spinal cord have been proposed. There are different types as well as degrees of spasticity. Clinical neurophysiologic recordings of reflex activity in patients with spasticity provide the means to differentiate among the various types of spasticity, to select the therapy most likely to be effective in a particular patient, and to see the results of its employment objectively. The latter will prove whether a specific therapy is useful or not. Ablative treatment at the level of the peripheral nerve or dorsal root may be useful, particularly when spasticity is severe. Drugs such as baclofen or diazepam relieve flexor spasms but are not particularly effective against spasticity itself. Dantrolene acts to weaken muscles, but that is not often helpful. Rarely do any of these therapies increase function; there are no effective cures for paresis or related negative manifestations of chronic spasticity.

Combined Modality Therapy↗
PubMed1986

Short-latency somatosensory-evoked potentials from radial, median, ulnar, and peroneal nerve stimulation in the assessment of cervical spondylosis. Comparison with conventional electromyography.

A study of data on 30 patients with cervical spondylosis was carried out to determine whether short-latency somatosensory-evoked responses (SEPs) to median, ulnar, radial, and peroneal nerve stimulation provided additional information to that obtained by electromyography (EMG), late responses, and peripheral conduction studies. Peripheral studies, EMG results and SEPs were within normal limits in ten patients with pain, but without objective neurological deficit. By contrast, of ten patients who had objective signs of root compression, conventional EMG results were normal in nine, but abnormalities of the SEPs from radial nerve stimulation were obtained in only five patients, and were normal from ulnar and median nerve stimulation. In ten patients with clinical features of myelopathy, seven had abnormal median SEPs and all had abnormal peroneal SEPs, whereas EMG results were abnormal in only five patients. It is suggested that SEPs and EMG are both of limited use in patients with only symptoms of root compression. In patients with signs of root compression, EMG is the most sensitive procedure; however, some additional information can be obtained from superficial radial SEPs. In patients with cervical myelopathy, SEP was the most useful procedure, especially when upper and lower limbs were studied.

Adult↗
PubMed1986

Early evolution and incidence of electroencephalographic abnormalities in Creutzfeldt-Jakob disease.

The clinical and EEG findings in patients in the literature with Creutzfeldt-Jakob disease (CJD) were reviewed and compared with findings in 36 patients with CJD at the Massachusetts General Hospital (MGH). Twenty-one of the 36 MGH cases had histopathology, all with findings consistent with CJD. EEGs in 18 patients studied pathologically and in 10 without pathological investigation (28 of the 36) had periodic sharp wave complexes (PSWC) at some time during the clinical course. Of the other eight patients, two had only a single EEG early in the course of the illness, four experienced unusually long clinical courses, and two never showed PSWC despite numerous EEGs. PSWC made their appearance within 12 weeks of onset of clinical symptoms in 25 of 27 in whom EEGs were done during that period. In the early stages, EEGs in 14 of 28 showed focal PSWC or amplitude asymmetries of PSWC that corresponded well with focal myoclonus or other focal neurological abnormalities. In the literature, PSWC occurred within 12 weeks of the onset of the illness in 66 of 75 patients (88%) with CJD who had comparable clinical and neuropathological findings and adequate EEG data during the first 3 months of the illness. In the approximately 10% of patients who experienced unusually long courses, PSWC occurred in only about 55%. The presence of PSWC in association with the appropriate clinical, biochemical, cerebrospinal fluid, and neuroradiological findings is diagnostic of CJD. Brain biopsy is, therefore, unnecessary even when clinical therapeutic trials are undertaken and certainty of diagnosis is required. The absence of PSWC in the EEG after 12 weeks' duration of illness is a point strongly against the diagnosis of CJD unless it is a rare subtype of long duration. Only those patients without PSWC need to be biopsied.

Adult↗
PubMed1986

Elastic properties of muscles measured at the elbow in man: II. Patients with parkinsonian rigidity.

A method is described to measure reproducibly stiffness, and therefore "tone", at the elbow of patients with Parkinson's disease using a torque motor. In Parkinsonian versus normal patients (previously reported) it was observed that: the neutral angle in Parkinson's disease patients was significantly smaller (92 degrees +/- 15 degrees) than in normals (107 degrees +/- 10 degrees), and in Parkinson's disease patients, even with relatively mild symptoms, the upper limb was stiffer than normals in the totally relaxed state with no electromyographic activity present. Our results suggest that changes in the passive mechanical properties of the upper limb affected by Parkinsonian rigidity may have taken place, accounting for the more flexed neutral elbow angle and greater passive stiffness. Using this technique, response to antirigidity therapy and natural progression of illness can be quantitatively assessed and followed.

Aged↗
PubMed1986

Asterixis: one type of negative myoclonus.

Asterixis is a disorder of motor control characterized by irregular myoclonic lapses of posture affecting various parts of the body independently. These lapses are caused by involuntary 50- to 200-msec silent periods appearing in muscles (even antagonistic groups of muscles) which are tonically active. That is, the silent periods and postural lapses occur in muscles that have been contracting for a time whether or not there has been slow shortening or lengthening but probably do not occur during or immediately after a sudden movement at a joint. What constitutes a sudden as opposed to a slow movement remains to be defined. When bilateral asterixis is present, one cannot rule out the possibility of a focal lesion (see Table 2), but it is almost always due to a metabolic encephalopathy (with a wide variety of possible causes). Unilateral asterixis is due to a localized lesion, perhaps otherwise not clinically evident, in the contralateral cerebral hemisphere. This episodic dysfunction within neural circuits which are normally concerned with maintenance of sustained or tonic muscle contraction may be released by focal lesions only in specific CNS areas (such as ventrolateral thalamus) or by a more generalized neurochemical imbalance (metabolic encephalopathies of various kinds). The system, a lesion or metabolic dysfunction which produces asterixis, is presumably an anatomically and/or pharmacologically distinct one; asterixis is not the result of a nonspecific disorder any more than are seizures. Presumably, those aspects of each of the different factors (e.g., subdural hematomas, drugs, electrolyte imbalance, cerebrovascular accidents, intracerebral tumors) that may produce asterixis or a seizure are mediated through some fundamental neuronal or neural systems process. To label asterixis or seizures nonspecific results of CNS disorders or results of nonspecific CNS disorders may be simply to avoid confronting our ignorance of the specific pathophysiologic mechanisms involved. Although the anatomy, neurochemistry, and physiologic function of this asterixogenic system remain to be elucidated, observations that asterixis may be caused by discrete anatomic or pharmacologic (e.g., phenytoin) lesions should tell us something important about mechanisms underlying sustained muscle contraction in humans. Unfortunately clinicoanatomic correlations alone cannot provide precise answers because even those reasonably focal vascular lesions that cause asterixis are too gross to permit localization or identification of the neural systems involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Brain↗
PubMed1985

Nocturnal enuresis: a review of treatment approaches.

Nocturnal enuresis, a common childhood problem, has several plausible etiologies: adverse environmental circumstances, psychologic disturbances and physiologic mechanisms. A wait-and-see approach is commonly adopted, since spontaneous resolution occurs in many children. Moderate success has been reported with the use of tricyclic antidepressants. Two behavioral conditioning approaches are reported to be highly successful in ameliorating enuretic episodes.

Antidepressive Agents, Tricyclic↗
PubMed1983

The investigation of traumatic lesions of the brachial plexus by electromyography and short latency somatosensory potentials evoked by stimulation of multiple peripheral nerves.

A study of 10 patients with brachial plexus trauma was performed to determine whether the diagnostic accuracy of sensory evoked potentials (SEPs) may be improved by using stimulation of multiple peripheral nerves (median, radial, musculocutaneous and ulnar). In addition, the relative advantages of SEPs and peripheral electrophysiological studies were considered. SEP patterns following most common brachial plexus lesions were predictable. Injuries to the upper trunk affected the musculocutaneous and radial SEPs predominantly. Lower trunk or medial cord lesions primarily affected ulnar SEPs. Diffuse brachial plexus lesions affected SEPs from all stimulation sites. In the majority of cases, the necessary information was obtainable from conventional EMG: however, for lesions involving the upper segments only, SEP techniques were more useful. It is suggested that selective SEPs from appropriate peripheral nerves when interpreted in combination with conventional EMG may add useful additional information.

Adolescent↗
PubMed1981

Late response and sural conduction studies. Usefulness in patients with chronic renal failure.

Late response (H reflex and F response) and sural conduction studies were used in addition to conventional motor and sensory conduction to detect peripheral neuropathy in 30 randomly selected patients with chronic renal failure (18 receiving hemodialysis), five of whom had no clinical evidence of peripheral neuropathy; 30 age-matched control subjects were also studied. Conventional motor (median, ulnar, peroneal, and tibial) and sensory (median and ulnar) nerve conduction studies showed abnormalities of motor conduction in 25 (83%) and of sensory conduction in 26 (87%) patients. Abnormalities of sural nerve conduction and of late responses were present in all 30 patients. Five patients (17%) who had normal routine motor conduction showed abnormalities of late responses in the same nerve distribution. All electrophysiologic abnormalities were significantly more evident in lower limbs. Studies of late responses and sural conduction, in addition to improving the diagnostic yield, provide a method whereby effects of dialysis and medical management can be followed quantitatively in patients whose neuropathy would otherwise be undetectable.

Action Potentials↗