A previously undescribed variant of the confluence of sinuses.

An 8-year-old female with a history of chronic headaches and uncertain papilloedema was found to have a variant of the posterior intracranial dural venous sinuses on magnetic resonance imaging assessment of the brain. Magnetic resonance venography included in the imaging revealed a circular formation of the confluence of sinuses and absent right-sided transverse sinus. The confluence of sinuses is a highly variable structure; however, to the authors' knowledge, a circular confluence of sinuses variant has not been reported in the literature.

Cerebral palsy. Mechanical evaluation and conservative correction of limb joint contractures.

Studies in animals and in children with cerebral palsy (CP) allow precise evaluation of the physiologic and pathophysiologic adaptations in muscle and tendon. In the individual child with CP, clinical evaluation must be much more precise than a routine examination in order to clearly define the nature of the contractures and select the correct therapeutic program.

[Close interdependence between passive and active soleus muscle torques in man: approach to the coregulation of the number of sarcomeres and length of the connective tissue]. / Etroite interdépendance entre les couples passifs et actifs du muscle soléaire chez l'homme: approche de la co-régulation du nombre des sarcomères et de la longueur du conjonctif musculaire.

Soleus muscle has, to as great an extent as possible, been functionally isolated in man. A device previously described permitted measurement of the soleus torque as a function of the tibia-calcaneum angle, and not as a function of tibia-foot angle. This latter angle cannot be correctly related to soleus length, since the arch of the foot can not be considered as rigid throughout the experiment. Ankle movements were performed on a horizontal plane by successive increments of 5 degrees from full extension (plantar flexion) up to full flexion (dorsiflexion). Passive torques were measured for every angle. At the same angles, the total torques were recorded while the subject exerted a voluntary constant contraction which corresponded to 45% of the maximum integrated electromyographical activity of soleus muscle. The active torque-angle curve was obtained by subtracting, for the same angle, the passive from the total torques. It must be stressed that, when the muscle is maximally shortened, little or no torque was measured. For the angle corresponding to the top of the sub-maximal active curve (integrated electromyographic activity 45% of the maximum), the passive torque was about 1.75 Nm and showed no significant interindividual variations. This result contrasted with the marked interindividual shifts which affect both passive and active curves. This interdependence of passive and active curves in human soleus muscle is compatible with the results of a previous study in the cat showing the concomitant adaptations of sarcomere number and connective tissue length.

Can vibration-induced illusions be used as a muscle perception test for normal and cerebral-palsied children?

Since poor control of muscle contractions in cerebral palsy may be due partly to defective processing of data originating from muscle, the need arose for a test as uncontaminated as possible by other afferent effects. For 18 normal children, vibration of the brachial biceps tendon always gave the illusion of elbow extension; when the triceps was vibrated the opposite illusion occurred. For 22 cerebral-palsied children the vibration test was successful for 26 elbows and failed for 18. These failures might provide a future explanation for certain therapeutic failures.

Adaptation of connective tissue length to immobilization in the lengthened and shortened positions in cat soleus muscle.

1. The aim of this study was to investigate length adaptation of connective tissue in adult cat soleus muscle immobilized in the lengthened position for 28 days (group I) or in the shortened position for 14 (group II) or 28 days (group II). 2. The method, combining passive tension-length curves of the whole muscle with measurement of the length of the contractile part of isolated fibres, enabled separate determination of length of the very slightly compliant tendinous part, and of the highly compliant parallel elastic component (PEC) mainly constituted of belly connective tissue. 3. PEC length was found to increase in group I and to shorten in group II and III, showing that it adapted to the length imposed on the muscle. 4. Tendinous part lengths did not change significantly in any of the three groups compared to the controls. 5. Comparison of the respective adaptations of PEC and contractile tissue lengths showed that PEC adaptation was insufficient in groups II and III.

Effects of muscle length on an increased stretch reflex in children with cerebral palsy.

No inhibitory influence of length on the increased stretch reflex was found in the internal gastrocnemius muscle of 19 cerebral palsied children. A facilitory influence of length was found in at least five patients in which quantitative data were obtained. These results were compared with previous data on a facilitory influence in the hamstrings and inhibitory influence in quadriceps muscles.

Muscle hypoextensibility in children with cerebral palsy: II. Therapeutic implications.

Twenty-nine children with cerebral palsy and triceps surae hypoextensibility were divided into 2 groups. In group I trophic regulation of the muscle was defective and in group II it was normal. Torque values were plotted against tibiocalcanean angles before and after treatment, which consisted of muscle lengthening by successive plaster casting or of surgical elongation of the tendon or the aponeurosis. In group I, casting had no effect, but surgery increased passive dorsiflexion and gave definite clinical improvement without modifying the range of passive muscle stretch. In group II, with normal muscle adaptation, plaster casts were successful when tolerated. Children in this group required braces after surgery to prevent rapid recurrence of hypoextensibility. Both casting and surgery increased the passive muscle stretch. There was a displacement of the starting point of the passive and active curves in both groups. This is an unavoidable side-effect which makes walking on tiptoes impossible after casting or surgery.

Muscle hypoextensibility in children with cerebral palsy: I. Clinical and experimental observations.

Extensibility of the triceps surae was compared in 12 normal children and in 21 children with cerebral palsy (CP). The latter group represented selected subjects who showed hypoextensibility in ischemia-tested noncontracting muscle, which is considered an indication of change in the physical properties of muscle. The difference between the 2 groups is illustrated by curves plotting torque of the noncontracting muscle against tibiocalcanean angles. Two measurements were found to be especially representative: 1) the angle related to a very slight torque and 2) the angle corresponding to a strong, standardized torque. In children with CP and with muscle hypoextensibility, both angles had abnormally high values and the difference between the 2 measurements was abnormally small. These findings indicate an insufficient range of passive muscle stretch, reflected by excessive steepness of the torque-angle curve. In normal children, maximal muscle contraction produces full plantar flexion; in some children with CP, contraction fails to produce any force in full plantar flexion. Instead, force is generated only at a smaller tibiocalcanean angle when the muscle reaches a sufficient length. These cases represent hypoextensibility with abnormally short muscle and abnormally long tendon. Data obtained by instrumental measurements can be reproduced with sufficient accuracy by appropriate clinical technique as described in this paper, and applied clinically, as described subsequently.

Experimental rapid sarcomere loss with concomitant hypoextensibility.

Slow soleus muscle in guinea pigs was actively shortened by constant electrical stimulation of the sciatic nerve for 12 hours. At the end of this period, hypoextensibility and a 25% decrease in the numbers of sarcomeres were observed. When a 36- or 48-hour period was allowed to elapse after the end of stimulation, some recovery occurred, and the sarcomere numbers were then found to be diminished by only 5%. If the stimulation was performed when the muscle was prevented from shortening (by ankle fixation in dorsiflexion), there was no decrease in sarcomere numbers and no hypoextensibility after neuroaxis lesions, when abnormal contractions maintain lasting shortening of the muscle.

Effects on torque angle curve of differences between the recorded tibia-calcaneal angle and the true anatomical angle.

The present study gives the results of a comparison of the recorded and true tibia-calcaneal angles in 17 normal subjects and in 14 patients with abnormally hypoextensible non contracting triceps. 1. For a minimal passive torque, the difference between true and recorded angles varied considerably from one individual to another. The mean and ranges for the two groups were respectively: -8 degrees (+7 degrees, -21 degrees) and -7 degrees (+5 degrees, -20 degrees). 2. When the passive torque increased as a result of slow passive lengthening of the muscle, the true curve was steeper than the recorded one, owing to differences between the two angle measurements. For each of the two groups the differences in means and ranges were respectively: 6 degrees (0 degrees, +13.5 degrees) and 8 degrees (3 degrees, 12 degrees). 3. Subjects made isometric voluntary contractions of the triceps surae at fixed angles which corresponded to step by step muscle lengthening. The resulting true curve was much steeper than the recorded curve. The differences in means and ranges were: 7 degrees (1.5 degrees, +15 degrees) in children of the two groups and respectively 3 degrees (0 degrees, +9 degrees) and 12 degrees (10 degrees, 14 degrees) in adults of the two groups. The present results show that this methodology was the only reliable way of correctly obtaining passive and active torque-angle curves, measuring differences between subjects, appreciating the effects of treatments and these by ascertaining whether or not trophic muscle regulation was defective.

Variation in the long-term results of elongation of the tendo Achillis in children with cerebral palsy.

Clinical assessment of equinus in children before and after operation was made over a twenty-year period (1958-1978), and three groups were defined. Forty-three muscles (Group I) had abnormal shortening without spasticity and the deformity progressed steadily despite immediate improvement after operation; this was considered to be the result of a lack of muscle growth during bone growth. Forty-one muscles (Group II) had both shortening and spasticity with an imbalance which might be unchanged after operation, or reversed or improved. Fourteen muscles (Group III) had spasticity only and progression was unpredictable and could not be defined. Improvement in gait was regularly observed in Group I in the early years after operation. In Groups II and III the results were variable. These results did not depend on surgical technique but on differences in pathophysiology.

Trophic muscle regulation in children with congenital cerebral lesions.

A decrease in sarcomere number and hypoextensibility of ankle extensors was observed in certain children with congenital cerebral lesions. This phenomenon was reproducible and reversible in normal animals, i.e. trophic regulation adapted the muscle to the imposed length. The form of the torque-ankle angle curve was studied in 30 children. Its modification after treatment was considered as a sign of muscle adaptation. This adaptation was present in one group of 14 children. The steepness of the curve increased or diminished depending on the initial disorder and the treatment administered. In another group, treatment failed to modify the shape of the curve. In certain cases trophic regulation of the muscle appeared to be absent.

The relationship between sarcomere length in the soleus and tibialis anterior and the articular angle of the tibia-calcaneum in cats during growth.

Sarcomere number and sarcomere length were studied in six groups of kittens ranging in age from 10 minutes to 5 months and compared with those of adult cats. Although the soleus muscle is a slow contracting muscle and the tibialis anterior a fast contracting muscle, both have previously been shown to have the same range relative to ankle movement. For a given angle of articulation the sarcomere length was found to be the same at all ages except perhaps for the newly born. In contrast, the sarcomere number differed considerably, being much higher in the older animals. The relationship between active tension and muscle length was also measured, and again no difference was found between the muscles at any age, although the shape of the curves for the soleus and tibialis anterior was different.

To what extent is the tibia-calcaneum angle a reliable measurement of the triceps surae length? Radiological correction of the torque-angle curve (III).

Previous papers gave some methods for the reliable measurement of the tibia-calcaneum angle. It is of common use to evaluate the physical properties of triceps surae on the basis of torque-angle curves. However this method is reliable only if each tibia-calcaneum angle corresponds to a defined distance between the insertions of the muscle in subjects of the same height. Evidence is given by radiological measurements that this correspondance is correct in normal children. However, this is no longer true in certain cerebral palsied children because of abnormal translation of the calcaneum and/or abnormal ratio of bone sizes. In this case the torque-angle curves do not define properly the torque-length curves. A method of correction is given. This correction may be as high as 15 degrees.

Functional adaptation of sarcomere number of normal cat muscle.

1. Physiological and histological data were obtained from soleus and tibialis anterior muscles of normal adult cats to study to what extent fibre length and sarcomere number varied between animals and how this was related to the physiological characteristics of the muscles. 2. For a given muscle, the variation in the sarcomere number of individual muscle fibres between animals was found to be about 25%. These difference could partly be explained by comparing the number of sarcomeres and the length of the fibula, which was chosen as an index of the size of the animal. The average sarcomere number in the tibialis anterior muscle was about 60% greater than in the soleus. The variations between animals and between the anterior tibialis and soleus muscles were significantly greater than the variations observed within the same muscle. 3. The sarcomere length is dependent upon the articular angle, that is to say, the length change imposed on the muscle. These length changes are more extensive in the soleus muscle (100%) than in the tibialis anterior muscle (60%). A very significant correlation was found between articular angle and sarcomere length (for soleus r = 0.98, for tibialis anterior r = 0.94). 4. Although fibre length did vary considerably within a given muscle, the sarcomere length showed only minor variations at any given angle. This suggests that sarcomere number is determined in each individual muscle fibre. Such an adaptation implies a concomitant adaptation of the tendinous part of the fibre. This adaptation, resulting in definite sarcomere length at a definite angle, has obvious physiological implications. 5. Conventional length vs. active tension curves were established for the soleus and the tibialis anterior muscles. It is suggested that the difference between the sarcomere number of the two muscles may result in the difference between the shape of curves of these two muscles. 6. Active torque-angle curves were established for the two muscles in situ. The shapes of the curves for soleus and tibialis anterior are similar in spite of the different mechanical conditions of the two muscles. This fact helps to explain why the two muscles, despite their similar articular range, had very different sarcomere number.