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The vestibular system, defined as the peripheral vestibular motion detectors and related central nervous system structures, senses motion in space and converts that motion into information that the remainder of the central nervous system can use to generate appropriate motor reflexes or facilitate complex processes such as the coordination of head, eye, and trunk movements or updating one's perception of his or her orientation in the world. The vestibular system, like the auditory system, converts physical stimuli into neural signals, but the vestibular system detects angular and linear acceleration, rather than sound. The vestibular system is present in all vertebrates and many invertebrates. Yet, despite the importance of spatial orientation in all mobile animals, the vestibular system is largely underappreciated until a malfunction occurs, at which point patients present to a physician, often an otolaryngologist, for treatment and education. This chapter discusses the anatomy of...

John H. Mills Samir S. Khariwala Peter C. Weber This chapter provides a brief summary of the most basic features of the anatomy and physiology of the ear. It is divided into sections on the external and middle ear, cochlea, and central nervous system (CNS). The focus is on the anatomic and physiologic bases of audition with an effort directed at functional features. Surgical anatomy, vasculature, and eustachian tube function are not discussed. External Ear The external ear consists of the pinna (auricle) and the external auditory canal from the meatus to the tympanic membrane (Fig. 129.1). The pinna of humans is composed mostly of cartilage and has no useful muscles. The center of the pinna, the concha, leads to the external auditory meatus, which is about 2.5 cm long. The lateral third of the canal is the cartilaginous portion. It contains cerumen-producing glands and hair follicles. The remaining medial two thirds is the bony portion, including an epithelial lining over the t...

The major mechanism of visual loss in glaucoma is retinal ganglion cell atrophy, leading to thinning of the inner nuclear and nerve fiber layers of the retina and axonal loss in the optic nerve. The optic disk becomes atrophic, with enlargement of the optic cup (see below). The iris and ciliary body also become atrophic, and the ciliary processes show hyaline degeneration. The pathophysiology of intraocular pressure elevation—whether due to open-angle or to angle-closure mechanisms—will be discussed as each disease entity is considered (see below). The effects of raised intraocular pressure are influenced by the time course and magnitude of the rise in intraocular pressure. In acute angle-closure glaucoma, the intraocular pressure reaches 60–80 mm Hg, resulting in acute ischemic damage to the iris with associated corneal edema and optic nerve damage. In primary open-angle glaucoma, the intraocular pressure does not usually rise above 30 mm Hg and retinal ganglion cell damage develops o...

A.Acute sinusitis The most commonly identified organisms in children with acute sinusitis are Streptococcus pneumoniae in 30% to 40%, Haemophilus influenzae in 20% to 25%, and Moraxella catarrhalis in 20%. In adults, S. pneumoniae and H. influenzae are the two leading causes of acute sinusitis, whereas Moraxella is unusual. Anaerobic organisms are primarily identified in cases of acute sinusitis originating from dental root infections, but are otherwise uncommon. Hospital-acquired sinusitis is most often seen as a complication of nasogastric tube placement, and is typically caused by gram-negative enteric organisms, such as Pseudomonas and Klebsiella species. B.Chronic sinusitis 1. Bacteria cultured from children with persistent symptoms are usually the same as those seen in acute disease. In children with more severe and protracted symptoms, anaerobic species (such as Bacteroides) and staphylococci are cultured more frequently. In adults with refractory symptoms, Staphylococcus epide...

All patients with mechanical valves require warfarin therapy. The risk of embolism is greater with a valve in the mitral position (mechanical or biological) than in the aortic position. With either type of prosthesis or valve location, the risk of emboli is higher in the first few days and months after valve insertion. Low-dose aspirin is recommended for all patients with prosthetic valves (see Table 1. For patients with mechanical valves, the addition of low-dose aspirin (80 to 100 mg/d) to warfarin therapy (INR 2.0 to 3.5) not only further decreases the risk thromboembolism but also decreases mortality due to other cardiovascular diseases. A slight increase in risk of bleeding with this combination should be kept in mind. Recommendations for Antithrombotic Therapy in Patients With Prosthetic Heart Valves Class I 1.First 3 months after valve replacement: Warfarin- INR 2.5 to 3.5 2.3 or more months after valve replacement: A. Mechanical valve AVR and no risk factor*: Bileaflet valve or...

SYMPTOMS AND SIGNS Type 1 diabetes Increased urination is a consequence of osmotic diuresis secondary to sustained hyperglycemia. This results in a loss of glucose as well as free water and electrolytes in the urine. Thirst is a consequence of the hyperosmolar state, as is blurred vision, which often develops as the lenses are exposed to hyperosmolar fluids. Weight loss despite normal or increased appetite is a common feature of type 1 when it develops subacutely. The weight loss is initially due to depletion of water, glycogen, and triglycerides; thereafter, reduced muscle mass occurs as amino acids are diverted to form glucose and ketone bodies. Lowered plasma volume produces symptoms of postural hypotension. Total body potassium loss and the general catabolism of muscle protein contribute to the weakness. Paresthesias may be present at the time of diagnosis, particularly when the onset is subacute. They reflect a temporary dysfunction of peripheral sensory nerves, which clears as in...

PATHOLOGY Detailed histological studies of pancreatic tissue are available from a limited number of cases of human acute pancreatitis. A histological spectrum of acute pancreatitis is recognized ranging from mild, interstitial disease to coagulation necrosis. 3 Interstitial pancreatitis may lead to local and systemic complications but is rarely fatal; necrotizing pancreatitis may be fatal in up to 30% of cases. Interstitial In interstitial pancreatitis the gland is edematous, but its gross architecture is preserved. Parenchymal inflammatory cells are present together with interstitial edema. Disruption of the normal acinar cell architecture is common and may contribute to the reduced enzyme secretion characteristic of acute pancreatitis. Zymogen granules are displaced from their fusion site in the apical domain of the cell and become dispersed throughout the cell, and the apical membrane appears contracted and microvilli disappear. 4 Zymogen granules fuse with each other instead of the...