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Lesions at and around the stylomastoid foramen are the commonest abnormality of the facial nerve [VII] and usually result from a viral inflammation of the nerve within the bony canal before exiting through the stylomastoid foramen. Typically the patient has an ipsilateral loss of motor function of the whole side of the...
A surgically induced Horner’s syndrome may be necessary for patients who suffer severe hyperhidrosis (sweating). This often debilitating condition may be so severe that patients are confined to their home for fear of embarrassment. Treatment is relatively straightforward. The patient is anesthetized and a bifurcate end...
Intraocular pressure will rise if the normal cycle of aqueous humor fluid production and absorption is disturbed so that the amount of fluid increases. This condition is glaucoma and can lead to a variety of visual problems including blindness, which results from compression of the retina and its blood supply. In the c...
Surfer’s ear, which is prevalent among individuals who surf or swim in cold water, results from the development of a “bony lump” in the external acoustic meatus. Growth of the lump eventually constricts the meatus and reduces hearing in the affected ear. In the clinic Although perforation of the tympanic membrane (eard...
“Blind puncture” of the subclavian and jugular veins to obtain central venous access used to be standard practice. However, subclavian vein puncture is not without complications. As the subclavian vein passes inferiorly, posterior to the clavicle, it passes over the apex of the lung. Any misplacement of a needle into o...
Immunological diseases may affect the thyroid gland and may overstimulate it to produce excessive thyroxine. These diseases may be associated with other extrathyroid manifestations, which include exophthalmos, pretibial myxedema, and nail changes. Other causes of diffuse thyroid stimulation include viral thyroiditis. S...
Level IV—from the inferior aspect of the cricoid to the top of the manubrium of the sternum and anterior to the posterior border of the sternocleidomastoid muscle. Level V—posterior to the sternocleidomastoid muscle and anterior to the trapezius muscle above the level of the clavicle. Level VI—below the hyoid bone and ...
Enlargement of the thyroid gland is due to increased secretion of thyroid-stimulating hormone, which is usually secondary to diminished output of thyroid hormones. The thyroid undergoes periods of activity and regression, which can lead to the formation of nodules, some of which are solid and some of which are partiall...
The recurrent laryngeal nerve lies close to the thyroid gland. It may be damaged in difficult surgical procedures, and this may produce unilateral spasm of the ipsilateral vocal cord to produce a hoarse voice. Since the thyroidectomy and institution of thyroxine treatment, the patient has lost weight and has no further...
A 25-year-old man complained of significant swelling in front of his right ear before and around mealtimes. This swelling was associated with considerable pain, which was provoked by the ingestion of lemon sweets. On examination he had tenderness around the right parotid region and a hard nodule was demonstrated in the...
Eighty-five percent of all strokes result from cerebral infarction, of which most are due to embolization. A duplex Doppler scan of the carotid vessels was performed. The majority of emboli originate from plaques that develop at and around the carotid bifurcation. Emboli consist of platelet aggregates, cholesterol, and...
The lesion cannot be a primary oculomotor nerve [III] nuclear injury. As both the pupillary reflexes and vision are affected, the lesion is likely to be along the course of the oculomotor nerve [III]. Medical conditions such as diabetes mellitus and vascular disease may produce an isolated oculomotor nerve [III] injury...
The visual pathways have now determined the site of the lesion. Visual information from the temporal fields is projected onto the medial aspect of the retina bilaterally. The visual information from the medial aspects of the retina is carried in fibers that cross the midline through the optic chiasm to the opposite sid...
During the third week of development the outermost layer of the embryo—the ectoderm—thickens to form a neural plate (eFig. 9.2A). This plate develops a longitudinally running neural groove, which deepens so that it is flanked on either side by neural folds (eFig. 9.2B). These folds further develop and eventually fuse d...
Neurons consist of a cell body (or soma), which contains the cell nucleus, short processes called dendrites for receiving input from other neurons, and long processes called axons, which conduct signals away from the cell body (eTable 9.2). Depending on their location, neuronal morphology can be quite variable. The maj...
The path to and from the cerebral cortex is achieved through various white matter pathways coursing through the spinal cord, brainstem, and cerebral hemispheres. Beneath the gray matter of the cortical surface is an expansion of white matter referred to as the corona radiata. This white matter pathway condenses to form...
Within the bony encasement of the skull and vertebral column, the CNS is surrounded by three concentric, connective tissue coverings called meninges (from Greek word meninx for “membrane”), which act to support and stabilize the brain and spinal cord. The focus of this section will be on the cranial meninges. The spina...
The two anterior cerebral arteries anastomose proximally via the anterior communicating artery, anterior to the optic chiasm (eFig. 9.22). Distal to this connection, the anterior cerebral artery (ACA) courses along the medial aspect of the cerebral hemisphere within the longitudinal fissure and follows the superior bor...
Running along the superior edge of the falx cerebri is the superior sagittal sinus. The superior sagittal sinus continues posteriorly to drain into the transverse sinuses bilaterally (eFig. 9.25A). Each transverse sinus turns inferiorly to form the sigmoid sinus, which exits the jugular foramen to become the internal j...
Because of its location deep within the brain, the thalamus is neighbored by several structures and also portions of the ventricular system. Anteriorly, the thalamus extends forward to contact the interventricular foramen, which connects the lateral and third ventricles (eFig. 9.28). Together, the thalamic nuclear mass...
The brainstem is a stalklike structure within the posterior cranial fossa of the skull connecting the forebrain and spinal cord (eFig. 9.31). From rostral to caudal, the brainstem consists of the midbrain, pons, and medulla oblongata. Broadly speaking, the brainstem has three main functions: (1) it is a conduit for tra...
The medulla is the longest portion of the brainstem, measuring approximately 3 cm in length (eFig. 9.32A). At the rostral connection of the medulla to the pons, it has a broad conical shape that tapers caudally before connecting with the spinal cord at the level of the foramen magnum. Along the midline of the anterior ...
At mid-pontine levels the superior cerbellar peduncles form the lateral walls of the expanding fourth ventricle (eFig. 9.38). Also at this level, the prominent middle cerebellar peduncles can also be seen, along with the motor nucleus and principal sensory nucleus of cranial nerve V, the trigeminal nerve. In the caudal...
At the level of the caudal pons, the anterior inferior cerebellar artery (AICA) branches off of the basilar artery and perfuses the lateral portion of the caudal pons (eFig. 9.43A). Rostral levels of the lateral pons are perfused by circumferential branches of the basilar artery (eFig. 9.43A and B). Medial portions of ...
The anterior and posterior surfaces of the spinal cord have several longitudinally running fissures and sulci. Along the midline on the anterior surface of the spinal cord is a deep separation, the anterior median fissure (eFig. 9.47). Posteriorly the spinal cord has a shallower separation, the posterior median sulcus,...
The anterolateral pathways are composed of three tracts: the spinothalamic, spinoreticular, and spinomesencephalic tract. Separate aspects of pain are conveyed through the spinothalamic tract, so we will follow the course of those neurons first. The first-order neuronal cell body of axons forming the spinothalamic trac...
Tracts of the lateral motor system include the lateral corticospinal tract and rubrospinal tract. Both are located in the lateral column of the spinal cord white matter and synapse on lower motor neuronal cell bodies in the lateral aspect of the anterior horn gray matter. Clinically, the most important tract is the lat...
Vestibulospinal tract axons arise from vestibular nuclei located in the pons and medulla. The medial vestibular nucleus gives rise to the medial vestibulospinal tract, which projects bilaterally to thoracic regions of the spinal cord, and the lateral vestibular nucleus gives rise to the lateral vestibulospinal tract, w...
The lentiform nucleus (Latin for “lens-shaped”) includes the globus pallidus and putamen, which appear lens-shaped when viewed laterally. Both of these structures are lateral to the internal capsule, which separates them from the thalamus and caudate nucleus medially (eFig. 9.58). Laterally, the putamen is bordered by ...
Within the posterior cranial fossa, the cerebellum is covered by the tentorium cerebelli of the dura mater (eFig. 9.17) and connects to the posterior surface of the brainstem via the superior, middle, and inferior cerebellar peduncles (eFig. 9.62). Anteriorly, the cerebellum forms the roof of the fourth ventricle (eFig...
Input from the spinal cord to the cerebellum conveys information from muscles and joints to influence muscle tone and posture. The primary spinal cord pathways with connections to the cerebellum include the anterior or ventral spinocerebellar and the posterior or dorsal spinocerebellar tracts. These tracts originate fr...
Although the retinal layer of the eyeball is often considered the beginning of visual perception, the anterior structures of the eye play an important role in visual perception too. The anteriormost structure is the cornea and is the first layer through which light, the visual stimulus, enters the eye (eFig. 9.72). Thi...
Continuing posteriorly, the optic tracts course around the midbrain to enter the lateral geniculate nucleus of the thalamus (eFig. 9.75). At this level, a small portion of the fibers from the optic tract travel to the pretectal area and superior colliculus to mediate the pupillary light reflex. Axons leaving the latera...
The first-order axons entering the brainstem from the cochlea terminate ipsilaterally on the dorsal and ventral cochlear nuclei. From here, second-order axons have several synaptic targets. Second-order axons forming the ascending auditory pathway ascend to the pons and project bilaterally on the superior olivary nucle...
The hypothalamus is a neuroendocrine organ that regulates physiological processes for survival such as consumption of fluid and food, temperature control, the sleep–wake cycle, growth, and reproduction. As a result of this vast array of functions, the nuclei of the hypothalamus make connections with several other neura...
The medial zone is divided into three regions: supraoptic, tuberal, and mammillary. There are four nuclei in the supraoptic region, which play a role in thermoregulation, osmoregulation, and the sleep–wake cycle. The supraoptic and paraventricular nuclei in this region synthesize antidiuretic hormone or vasopressin, wh...
After synapsing with the mitral cells in the glomeruli of the olfactory bulb, mitral cell axons converge to form the olfactory tract. The olfactory tract then divides into medial and lateral olfactory striae to reach different synaptic targets (eFig. 9.94). Some of the axons in the medial olfactory striae travel throug...
The septal region is located rostral to the anterior commissure along the medial aspect of the cerebral hemispheres (eFig. 9.99). This region appears to play a role in pleasurable behaviors. Conversely, lesion studies indicate that damage to this area evokes behaviors of extreme displeasure or rage. Afferent axons to t...
Through this section we have described a collection of anatomical structures and defined their connections with other areas of the brain and brainstem without exploring how these individual structures are interconnected with one another. In the 1930s James Papez, an American neurologist, described a circuit that links ...