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L J Bour

Publications and source records attributed to L J Bour.

At least 37 records · Page 2Linked to original sources
PubMed1994

Clinical and electromyographic features of levator palpebrae superioris muscle dysfunction in involuntary eyelid closure.

We report on five patients with involuntary eyelid closure, diagnosed as blepharospasm and referred to use for treatment with botulinum A toxin. Synchronous electromyographic (EMG) recording was performed from the levator palpebrae superioris (LP) and the orbicularis oculi (OO) muscles. In the first two cases, EMG registration showed alternating, semirhythmic dystonic activities in both the LP and OO, clinically perceptible as "flickering" of the eyelids. While the eyelids were lowered, one of them also showed involuntary upper eyelid tractions due to dystonic activities of LP. In the third patient, EMG patterns were characterized by a gradual decrease in the level of LP activity, followed by the contraction of OO, which facilitated the return of LP to its tonic activity, termed "postinhibition potentiation" of LP. In the fourth patient, EMG recording showed involuntary inhibition of LP in combination with blepharospasm. Involuntary closure of the eyelids in the fifth patient was caused by short or prolonged periods of involuntary LP inhibition, whereas OO activity remained normal. Our results provide further evidence that LP muscle activities are regulated by burst-tonic motoneurons, and we suggest that these motoneurons, and/or the input signals regulating their activities, can be involved independently in a pathological process. Clinical symptoms are discussed that may be helpful to recognize those cases with LP motor dysfunction, whether or not accompanied by OO activity disorders. Because the term blepharospasm indicates an abnormal motor function of OO, we propose "blepharospasm-plus" to designate those cases with a combined motor dysfunction of LP and OO muscles.

Aged↗
PubMed1994

Modeling motoneuron firing properties: dependency on size and calcium dynamics.

The origin of functional differences between motoneurons of varying size was investigated by employing a one-compartmental motoneuron model containing a slow K+ conductance dependent on the intracellular calcium concentration. The size of the cell was included as an explicit parameter. Simulations show that motoneurons of varying size cannot be regarded as simple 'scaled' versions of each other. Rather, they are expected to have intrinsic properties that vary with cell size. These intrinsic properties refer to the membrane conductances per unit area and the dynamics of the intracellular calcium concentration.

Calcium↗
PubMed1994

Normalization of soleus H-reflex recruitment curves in controls and a population of spastic patients.

We examined soleus H-reflex recruitment in 30 controls and 33 patients with spinal cord lesions and spastic spinal paresis. H-reflex gain and threshold were determined from recruitment curves after normalization of stimulus intensity as a multiple of the current for a threshold M-response. Reflex gain was expressed as the mean slope of the H-reflex recruitment curve up to the half-maximal response size. Up to this point the curve follows an almost linear trajectory and will mainly reflect Ia afferent stimulation. This slope had a large variability but was clearly correlated with the H/M ratio. The mean gain was equal in controls and patients. The relation between H- and M-thresholds was expressed as a ratio which had a lower mean value in the patients. Though both H- and M-thresholds may be influenced by peripheral factors, this lower ratio suggests an increase in spinal motoneuron excitability in patients.

Adolescent↗
PubMed1994

Independence of soleus H-reflex tests in control and spastic subjects shown by principal components analysis.

Different soleus H-reflex tests are used in the study of neurophysiological mechanisms of motor control. We studied the interdependence pattern of a number of soleus H-reflex tests, i.e., vibratory inhibition, the ratio of the reflex response to direct muscle potential (H/M ratio) and the homonymous recovery curve with a principal components analysis in 48 healthy controls and 38 patients with signs of the upper motoneuron syndrome. In controls, the analysis showed 3 independent principal components (PCs). Vibratory inhibition and H/M ratio loaded on separate components. Late facilitation and late inhibition variables of the recovery curve loaded on the third component due to the positive correlation (P < 0.001) between these variables. In spastic patients the analysis identified 4 independent PCs corresponding with vibratory inhibition, H/M ratio, late facilitation and late inhibition variables, respectively. The findings suggest that the mutual independence of the different soleus H-reflex tests in patients with the upper motoneuron syndrome has retained the control situation to a large extent.

Adolescent↗
PubMed1994

Electromyographic features of levator palpebrae superioris and orbicularis oculi muscles in blepharospasm.

Electromyographic (EMG) recording was performed synchronously from the levator palpebrae superioris (LP) and the orbicularis oculi (OO) muscles in 28 patients referred to us for treatment of blepharospasm with botulinum A toxin. At the time of this study, 19 patients were under the treatment with botulinum, four started treatment shortly after the EMG recording and five patients had not yet been treated. Based on the EMG patterns, we were able to classify five major groups of abnormalities. Group 1 (blepharospasm): consisted of 10 patients with dystonic discharges limited to OO, normal LP tonic activity, intact reciprocal inhibition between LP and OO and dense bursts of action potentials with high amplitude preceding the return of LP tonic activity, i.e. 'postinhibition potentiation' of LP, brought about by a brief contraction of OO. Group 2 (combined dystonic activities of LP and OO): seven patients belonged to this group. The EMG recording revealed alternating tremulous discharges in both LP and OO muscles, and short intervals of co-contractions due to moderately disturbed reciprocal inhibition. Group 3 (combination of blepharospasm, LP motor impersistence): the EMG patterns, observed in three patients, were characterized by a gradual cessation of LP activity, followed by a brief contraction of OO, which facilitated the return of LP activity, resulting in opening of the eyes. The EMG recordings, thus, revealed the crucial, beneficial role of postinhibition potentiation as a compensatory mechanism in this type of eyelid movement disorder. The EMG patterns were also characterized by short or prolonged periods of dystonic discharges limited to the OO muscles. Group 4 (combination of blepharospasm, involuntary LP inhibition): this group consisted of four patients. In addition to episodes of dystonic activities of OO, the EMG also showed some periods of involuntary inhibition of LP without any concomitant activities of OO. Two patients also exhibited a failure of inhibition of OO muscle activity, following the voluntary contraction of this muscle. The postinhibition potentiation was often not observed. Group 5 (involuntary LP inhibition): consisted of four patients with EMG patterns of involuntary inhibition of LP activity, without any dystonic discharges in OO. The postinhibition potentiation was not observed in this group. The response to the treatment with botulinum toxin was good in the first group and gradually worsened towards the fifth group. Application of botulinum into multiple sites of OO, especially its pretarsal portion, resulted in better response to the treatment in the second and fourth groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

Abnormal eye movements in blepharospasm and involuntary levator palpebrae inhibition. Clinical and pathophysiological considerations.

We report on four patients with involuntary eyelid closure and eye movement disorders. Three were healthy until the onset of their illness and one had a mild generalized choreoathetosis and dystonia due to kernicterus. Electromyographic recording revealed solely blepharospasm in two patients and blepharospasm in combination with involuntary levator palpebrae inhibition in the other two. The eye movement abnormalities were clinically characterized by inability to fix gaze and short or prolonged episodes of uncontrollable eye deviations accompanied, in two patients, by diplopia in horizontal or vertical directions. These episodes occurred independently of a disorder of eyelid movement. Eye movement recordings with a double magnetic induction technique showed saccadic intrusions in horizontal directions. They consisted of highly frequent square wave jerks in three and sporadic macro-square wave jerks in two patients. There were also episodes of extraocular muscle dystonia, commonly known as oculogyric crises, resulting in involuntary upward eye deviation in all patients and lateral deviation in three patients. In one patient, nasal-ward deviations were sometimes restricted to one eye. We conclude that these abnormal eye movements do not necessarily point to a symptomatic form of dystonia and that they may limit the beneficial effect of botulinum toxin or surgical intervention in the therapeutic management of involuntary eyelid closure. We suggest that either basal ganglia, especially substantia nigra pars reticularis and the brainstem structures, especially the paramedian pontine reticular formation, or both, may be involved in the pathogenesis of these abnormal movements.

Adult↗
PubMed1993

Spectral analysis of the EEG and 99m-Tc-HMPAO SPECT-scan in Alzheimer's disease.

99m-technetium-hexamethylpropylene-amineoxine (99m-Tc-HMPAO) single-photon-emission-computer-tomography (SPECT)-scans and spectral analyzed electroencephalogram (EEGs) of 20 patients with Alzheimer's disease (AD) were studied. A significant correlation was found between the temporoparietal-cerebellar-ratio (TP/C-ratio) of the SPECT-scan and the peak frequencies of leads T3-T5, C3-P3, and C4-P4 of the EEG. In addition a significant negative correlation between the TP/C-ratio and the theta/alpha-ratio (t/a-ratio) of leads T3-T5, T4-T6, C3-P3, and C4-P4 was demonstrated. Our study demonstrates that slowing of the EEG parallels a decrease in blood flow in the temporoparietal regions in AD-patients. Both findings could be parallel phenomena of regional hypometabolism.

Adult↗
PubMed1993

Posterior tibial nerve somatosensory evoked potentials in slowly progressive spastic paraplegia: a comparative study with clinical signs.

Clinical and neurophysiological examinations were performed on seven patients with hereditary spastic paraplegia and on eight patients with primary lateral sclerosis. The results were compared with those obtained from a group of 39 control subjects. Prolonged latency times and decreased amplitudes of the posterior tibial nerve (PTN) somatosensory evoked potentials (SEPs) were found in the majority of the patients. The SEP changes occurred without sensory impairment or with loss of vibration sense only. There was no significant relation between the PTN SEP abnormalities and the severity of pyramidal signs for the whole patient group, nor longitudinally for the individual subjects. Analyses of PTN SEPs in patients suffering from slowly progressive spastic paraplegia (SP), therefore, seem to be a method to indicate a feature of spinal cord dysfunction that is not related to the severity of clinical signs. Considering the neuropathology of the spinal cord in SP patients, we furthermore argue that the ascending spinal pathway involved in conducting impulses for PTN SEPs probably uses other routes as well as the funiculus gracilis.

Adolescent↗
PubMed1993

Soleus H-reflex tests and clinical signs of the upper motor neuron syndrome.

Soleus H-reflex tests are used for elucidating pathophysiological mechanisms in motor control. The cumulative vibratory inhibition of the soleus H-reflex, the ratio of the reflex to direct muscle potential (H to M ratio) and the recovery curve of the soleus H-reflex were studied in 38 patients with varying signs of the upper motor neuron syndrome for a possible relation with clinical features. The results were compared with those obtained from a group of healthy volunteers. The magnitude of vibratory inhibition decreased with increase of hypertonia. The H to M ratio increased as the activity of the tendon reflex was enhanced and correlated to a lesser degree with muscle tone. Both the H to M ratio and late facilitation of the soleus H-reflex recovery curve were elevated in clonus. The findings suggest that alterations in the results of soleus H-reflex tests relate to specific clinical features of the upper motor neuron syndrome. Possible pathophysiological implications are discussed.

Adolescent↗
PubMed1991

Covering one eye in fixation-disparity measurement causes slight movement of fellow eye.

In the subjective measurement of fixation disparity (FD), the subject fuses contours presented in the peripheral macular areas of both eyes (fusion lock). The position of the eyes relative to each other is monitored by means of two haploscopically seen vertical lines presented in the central macular area, one above and one below a binocularly seen horizontal line. The subject is instructed to shift one of the vertical lines horizontally until the two are aligned, while fixating their intersection with the horizontal line. It has recently been questioned whether the foveolae really are pointed towards the perceived intersection. In this study, we monitored the position of one eye while intermittently covering the fellow eye, while the subject maintained fixation of the intersection of the remaining vertical line and the horizontal line. We found slight differences in position of the measured eye, depending on whether the other eye was covered or not, i.e. depending on the presence or absence of fusion in the macular periphery. These differences were more pronounced in the non-dominant eye.

Adult↗
PubMed1991

EEG artefacts caused by a Clinitron bed.

Clinitron beds, often used to prevent decubitus ulcers, may cause an EEG artefact by static electricity. The best way to prevent this artefact is to turn off the bed during EEG registrations.

Beds↗
PubMed1991

[Behavior of the other eye in measuring fixation disparity].

In the subjective measurement of FD, the proband fuses contours presented in the peripheral macular areas of both eyes ('fusion lock'). The position of both eyes relative to each other is monitored by means of two haploscopically seen vertical lines presented in the central visual field, one above and one below a binocularly seen horizontal line. The subject is instructed to shift one of the vertical lines horizontally until the two are aligned, while fixating their intersection with the horizontal line. It has recently been questioned whether the foveolae really are pointed at the perceived intersection. To investigate this matter, we registered the position of one eye while intermittently covering the fellow eye, while the subject maintained fixation of the intersection. We found slight differences in monocular eye position depending on the presence or absence of fusion in the macular periphery, confirming earlier findings in part. These differences were more pronounced in the nondominant eye.

Adult↗
PubMed1989

Cumulative vibratory indices and the H/M ratio of the soleus H-reflex: a quantitative study in control and spastic subjects.

Suppression of the soleus (Sol) H-reflex recruitment curve by Achilles tendon vibration and the ratio of maximum Sol H-reflex (Hmax) to maximum M-response (H/M ratio) have been studied by means of computer processing on the basis of peak-to-peak (P-P) and area values in 46 controls and in 16 spastic patients. The 'classical' vibratory index (VI) has been compared with a new cumulative VI (CVI), which is defined as the quotient of the surface under the recruitment curve obtained with vibration and the one obtained without vibration up to an equal intensity level. Statistical analyses were performed from threshold to 3 different intensity levels. Tendon vibration is found to be less effective at higher intensity levels. Mean values with S.D.s of CVIs at Hmax intensity are significantly lower than those of the 'classical' VIs. VIs increase with age while H/M ratios decline. Stepwise discriminant analyses showed that area CVI at Hmax intensity yielded the best distinction between controls and patients. Additional differential contribution is obtained by P-P H/M ratio. A canonic variable derived from these two variables correctly classified 44 out of 46 controls and 15 out of 16 patients. The methods presented improve the specificity of the quantitative neurophysiological measure of spasticity by means of Sol H-reflex recordings.

Achilles Tendon↗
PubMed1988

Digital nerve somatosensory evoked potentials and flexor carpi radialis H reflexes in cervical disc protrusion and involvement of the sixth or seventh cervical root: relations to clinical and myelographic findings.

Peak latencies of somatosensory evoked potentials (SEPs) from nerves of the first digit (digit 1-SEP), 39 controls, and third digit (digit 3-SEP), 47 controls, and indicated for Erb's point, second cervical vertebra (Cv2) and contralateral cortical hand area correlated significantly with arm length. Single regression analysis for arm length for Erb's potentials and the Cv2 potential in digit 1-SEP, and multiple regression analysis for arm length and age for the Cv2 potential in digit 3-SEP, the cortical potentials and flexor carpi radialis H reflex were used for demonstration of root C6 or C7 pathology. Upper crossing of +3 S.D. was defined as abnormal. The combined examination yielded abnormalities in 81% of our 22 patients operated for compression of root C6 or C7 due to cervical disc protrusion. A minority of the patients showed multiple positive correlations between symptoms and electrophysiologic and myelographic findings. In others only one or the other investigative procedure provided confirmatory information, while, in a notable number (6 patients), these approaches revealed abnormalities when there were no or non-specific symptoms. The presented electrophysiological investigations are useful to determine the presence and severity of root C6 or C7 compression as well as the functional relevance of a myelographic abnormality.

Adult↗
PubMed1987

The flexor carpi radialis H-reflex in polyneuropathy: relations to conduction velocities of the median nerve and the soleus H-reflex latency.

In 80 controls latencies of flexor carpi radialis (FCR) and in 94 controls latencies of soleus H-reflexes correlated well with length of the extremity, body height and age. Multiple regression equations using latency as a variable dependent on age and body height can be best used in practice when both reflexes are employed for demonstration of proximal pathology. The majority (69%) of 93 patients with various polyneuropathies showed abnormalities in both reflexes illustrating that proximal nerve segments are frequently involved. Four per cent had abnormal FCR H-reflexes with normal soleus H-reflexes whereas the reverse was found in 19% of the patients. Abnormal FCR H-reflexes occurred with normal motor and sensory conduction velocities in the peripheral part of the median nerve in 14%, whereas the reverse was seen in 12%, indicating that FCR H-reflex examination is a valuable supplement to conventional conduction studies for detection of electrophysiologically existing pathology.

Action Potentials↗