Figure 10-6. Cervical disc herniation as visualized with T2-weighted MRI. A. Parasagittal view of a large posterior disc extrusion at C6-C7. Smaller broad-based posterior disc bulges are seen at C4-C5 and C5-C6. B. Axial view of the large right posterolateral disc extrusion shown in (A) at C6-C7 (arrow) causing severe narrowing of the right neural foramen and compression of the exiting C7 nerve root. C. By way of contrast, an axial view of the broad-based posterior disc bulge at C4-C5 (arrows) causes only minimal narrowing of the spinal canal and no compression of the spinal cord.
Figure 10-7. Course of the brachial plexus and subclavian artery between the anterior scalene and middle scalene muscles. Dilatation of the subclavian artery just distal to the anterior scalene muscle is illustrated. Immediately distal to the anterior and middle scalene muscles is another potential area of constriction, between the clavicle and the first rib. With extension of the neck and turning of the chin to the affected side (Adson maneuver), the tension on the anterior scalene muscle is increased and the subclavian artery compressed, resulting in a supraclavicular bruit and obliteration of the radial pulse.
Chapter  10    Pain in the Back, Neck, and Extremities
Disorders of the Special Senses
CHAPTER 11  Disorders of Smell and Taste
CHAPTER 12  Disturbances of Vision
CHAPTER 13  Disorders of Ocular Movement and Pupillary Function
CHAPTER 14  Deafness, Dizziness, and Disorders of Equilibrium
The four chapters in this section are concerned with the clinical aspects of the highly specialized functions of taste and smell, vision, hearing, and the sense of balance. These special senses and the cranial nerves that subserve them represent the most finely developed parts of the sensory nervous system. Dysfunctions of the eye and ear are, of course, the domain of the ophthalmologist and otorhinolaryngologist, but they also are of great interest to the neurologist. Some defects in the special sensory apparatus reflect the presence of systemic disease and others represent the initial or leading manifestation of neurologic disease. In keeping with the general scheme of this text, the disorders of the special senses and of ocular movement are discussed in a particular sequence: first, certain facts of anatomic and physiologic importance, followed by cardinal clinical manifestations of disease, and then the syndromes of which these manifestations are a part.
Disorders of Smell and Taste
The sensations of smell (olfaction) and taste (gustation) are suitably considered together. Physiologically, these modalities share the singular attribute of responding primarily to chemical stimuli; that is, the end organs that mediate olfaction and gustation are chemoreceptors. Also, taste and smell are interdependent clinically, as the appreciation of the flavor of food and drink depends to a large extent on its aroma, and an abnormality of one of these senses is frequently misinterpreted as an abnormality of the other. In comparison to sight and hearing, taste and smell play a less critical role in the life of the individual. However, chemical stimuli in communication between humans are probably very important for some functions that have not been fully explored. Pheromones (pherein, “to carry”; hormon, “exciting”), that is, odorants exuded from the body, as well as perfumes, play a part in sexual attraction; noxious body odors may repel. In certain vertebrates the olfactory system is remarkably well developed, rivaling the sensitivity of the visual system. Though humans were thought to be capable of discriminating as many as 10,000 different odorants based on work by Reed and others, recent experimental studies by Bushdid and colleagues have shown that this may be a vast underestimation.