Cerebrospinal fluid (CSF) fistulas are characterized by the egress of CSF from the intracranial cavity through an osteodural disruption between the subarachnoid space and a pneumatized structure within the skull base. Depending on the cause, CSF fistulas are classified as acquired or congenital, and acquired fistulas are further classified as traumatic, nontraumatic, or spontaneous. Spontaneous CSF fistulas are considered to result from a multifactorial process and have been postulated to represent a variant of idiopathic intracranial hypertension. However, an anatomic predisposition involving thinning of the cranial base, such as pneumatization of the sinus walls, must also be present. This process creates areas of structural weakness that act as potential pathways for CSF leaks, which most commonly occur in the ethmoid roof, sphenoid sinus, and temporal bone. Because CSF leaks may be overlooked, a result of their asymptomatic or subtle, intermittent course, a high level of suspicion is crucial in making an early diagnosis. However, CSF fistulas may be well seen at computed tomography (CT), which depicts bone defects, and magnetic resonance cisternography, which reveals the contents of herniated tissue. Knowledge of the location and size of the bone defect and herniated contents is crucial for the selection of surgical approach and grafting material.
We propose the existence of a dual visual language route in the left dominant hemisphere. The first pathway seems to run basally, from the occipital lobe to the posterobasal temporal cortex, mediated by the left inferior longitudinal fascicle, subserving visual recognition. The second pathway might run superiorly and more medially, from the occipital pole directly to the frontal areas, and could be underlain by the inferior fronto-occipital fascicle, involved in naming (semantic processing). Such a model might have both fundamental and clinical implications for the selection of the tasks during awake mapping as well as for postsurgical rehabilitation.
The study aimed to describe in cat forelimb and shoulder motoneurones the convergence and projection patterns from large muscle spindle afferents (Ia). In 11 chloralose‐anaesthetized cats maximum Ia EPSPs evoked by electrical stimulation of ipsilateral forelimb nerves were obtained in 309 intracellularly recorded α‐motoneurones.
Groups of motor nuclei displayed similar Ia patterns. As in the distal forelimb they were often interconnected by bidirectional pathways, which were used to combine Ia synergistic groups. Three such groups are described at the shoulder.
The first group was composed of the main flexors of the scapulo‐humeral joint. Regular disto‐proximal Ia excitation from elbow extensors (and median afferents) indicates a coupling of flexion in the scapulo‐humeral joint to the angular position of the elbow.
The second group comprised the outward rotators of the humerus with differentiated Ia convergence onto the different group members. The patterns of Ia excitation received and sent by the group members demonstrate that the outward rotators are incorporated in versatile synergisms and may occupy a central position in steering forelimb movements.
The third group was formed by the spinatus muscle and the subscapularis. This arrangement is suggested by the common convergence onto them from the elbow extensors and flexors. The pattern may serve to guide and keep the humeral head in the joint capsule.
The Ia synergistic groups receive Ia convergence from muscles acting at distant joints and also project to distant muscles. This is discussed as part of an extended pattern of Ia connections along the forelimb. In this way the shoulder muscles would be incorporated in flexor and extensor oriented synergisms which are needed to co‐ordinate the muscular activation along the multijoint forelimb during locomotion. When the shoulder Ia pathways are compared with those in the distal forelimb, organization of the Ia system apparently follows a few basic principles which have adapted to the mechanical situation at the particular joints and their mechanical interaction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.