The cranial nerves

With the exception of the olfactory and optic nerves, all cranial nerves enter or leave the brain stem. Three of the cranial nerves are purely sensory (I, II and VIII), five are motor (III, IV, VI, XI and XII) and the remaining nerves (V, VII, IX and X) are mixed. The olfactory nerve will be discussed in Chap. 14, the optic nerve in Chap. 8 and the cochlear nerve in Chap. 7. The nuclei of the cranial nerves are arranged in an orderly, more or less columnar fashion in the brain stem: motor nuclei, somatomotor, branchiomotor and visceromotor (parasympathetic), derived from the basal plate, are located medially, whereas sensory nuclei, somatosensory, viscerosensory and vestibulocochlear, derived from the alar plate, are found lateral to the sulcus limitans. The cranial nerves innervate structures in the head and neck as well as visceral organs in the thorax and abdomen. The cranial nerves control eye movements, mastication, vocalization, facial expression, respiration, heart rate and digestion. One or several of the cranial nerves are often involved in lesions of the brain stem, of which the location can usually be determined if the topographical anatomy of the cranial nerves and their nuclei is known. Several examples are shown in Clinical cases. Following a few notes on the development of the brain stem and congenital cranial dysinnervation disorders (Sect. 6.2), the following structures will be discussed: (1) ocular motor nerves and the effects of lesions of individual ocular motor nerves (Sect. 6.3); (2) eye movements and some disorders affecting them (Sect. 6.4); (3) the trigeminal nerve and changes in the blink reflex (Sect. 6.5); (4) the facial nerve and peripheral facial nerve paralysis (Sect. 6.6); (5) the gustatory system (Sect. 6.7); (6) the vestibulocochlear nerve, vestibular control and some peripheral and central vestibular syndromes (Sect. 6.8); and (7) the last four cranial nerves and some disorders affecting them (Sects. 6.9 and 6.10). The English terms of the Terminologia Neuroanatomica are used throughout.</p

Therapeutic mechanisms of a mindfulness-based treatment for IBS: effects on visceral sensitivity, catastrophizing, and affective processing of pain sensations

Irritable bowel syndrome (IBS) is a prevalent functional disorder characterized by abdominal pain and hypervigilance to gastrointestinal sensations. We hypothesized that mindfulness training (MT), which promotes nonreactive awareness of emotional and sensory experience, may target underlying mechanisms of IBS including affective pain processing and catastrophic appraisals of gastrointestinal sensations. Seventy five female IBS patients were randomly assigned to participate in either 8 weeks of MT or a social support group. A theoretically grounded, multivariate path model tested therapeutic mediators of the effect of MT on IBS severity and quality of life. Results suggest that MT exerts significant therapeutic effects on IBS symptoms by promoting nonreactivity to gut-focused anxiety and catastrophic appraisals of the significance of abdominal sensations coupled with a refocusing of attention onto interoceptive data with less emotional interference. Hence, MT appears to target and ameliorate the underlying pathogenic mechanisms of IBS