Syndromes Primarily Involving Hearing

Hearing loss is highly prevalent, especially in the older population, and three types are commonly encountered conductive, sensorineural, and central hearing loss. In conductive hearing loss, sound is not transmitted into the inner ear. Diagnosis is ordinarily made via observation of an air-bone gap on audiometry, meaning that hearing is superior when sound is transmitted in such a way that it bypasses the middle ear ossicular chain. Causes include a buildup of ear wax, foreign body in the ear...

Evaluation Guidelines

In virtually every patient who presents with overt or subtle manifestations of trigeminal nerve dysfunction, some form of laboratory evaluation is indicated ( Table 10-2 ). Careful and directed neurological examination dictates the most important tests to obtain. Neuroimaging. Once a lesion has been reasonably localized to the cortex, white matter pathways, thalamus, or brain stem, neuroimaging is essential to support a definitive clinical diagnosis (for complete text, see reference 'i )....

Strychnine

Excessive and spontaneous release of acetylcholine acetylcholinesterase and pseudoCholinesterase Central analeptic agent GABA antagonist postsynaptic inhibitor Blood low Cholinesterase activity (70 of baseline) Pulmonary and dermal irritant renal effects pulmonary effects cardiac effects GI distress garlic or rotten fish odor Metallic taste thirst burning eyes GI distress excessive sweating and salivation hypothermia liver dysfunction Mania hallucinations delinum headache vertigo cognitive...

Neurofibroma

Both types of neurofibroma are associated with a gene localized to chromosome 17q11.2 for NFI y and to chromosome 22 for NFII. The NFI gene encodes a protein termed neurofibromin that is involved in regulation of the RAS protein. Epidemiology and Risk Factors. Neurofibromatosis (NFI), also known as von Recklinghausen's disease, comprises a constellation of tumors of the CNS. NFII is defined by bilateral acoustic neuromas. Patients with NFI have an increased...

Clinical History

Patients with dysfunction of structures innervated by CN XI or XII or their supranuclear input may present to the physician with various complaints. The more common complaints when CN XI is involved are difficulty rotating the head, complaint that the head droops forward, or complaint that the shoulders seem asymmetrical or misshapen. The more common complaints when CN XII is involved are slurred speech, garbled speech, speaking with marbles in my mouth, difficulty chewing, complaints that my...

Hypocapnia

Hyperventilation is defined as breathing in excess of metabolic demands and, therefore, is purely a respiratory disturbance. It produces hypocapnia, respiratory alkalosis, cerebral vasoconstriction (which, in turn, reduces the CBF), a reduction in the availability of O 2 peripherally (through shifts of the O 2 dissociation curve), a reduction in the level of ionized serum Ca, and when sustained, significant hypophosphatemia. y Thus, neurological features are frequent, and patients with...

Overview

The cerebellum is located behind and below the cerebral hemispheres, overlying the brain stem. It is separated from the cerebral hemispheres by the tentorium cerebelli, a membranous structure. The cerebellum consists of two large hemispheres and a midline structure, the vermis. Midline structures are involved in the control of motor execution, balance, and eye movements, and the lateral parts of the hemispheres are involved in motor planning. Lesions of the midline structures result in...

Transient Ischemic Attacks TIAs

A TIA is a transient episode of focal neurological or retinal dysfunction secondary to impaired blood supply in a vascular territory. Clinical signs typical of TIAs in the carotid and vertebrobasilar territories are outlined in T,aMe.2.2-2 . It should be noted that transient vertigo, diplopia, dysarthria, or dysphagia in isolation is insufficient to establish a diagnosis of vertebrobasilar TIAs. In addition, isolated drop attacks in which the patient falls to the ground, maintains...

Neurocysticercosis

Neurocysticercosis is considered the most common parasitic disease of the CNS. In countries where this infection is endemic, it is the most common cause of late-onset epilepsy. Humans acquire cysticercosis by the ingestion of food contaminated with Taenia solium eggs, most often undercooked pork but also water and vegetables contaminated with human feces. '124 Pathogenesis and Pathophysiology. After food contaminated with T. solium eggs is ingested, the eggs hatch...

Strachans Syndrome

In 1888, Henry Strachan, a British medical officer stationed in Jamaica, described a syndrome of painful peripheral neuropathy, ataxia, optic neuropathy, and stomatitis among sugar cane workers. Denny-Brown and others found similar ailments among allied troops liberated from prisoner-of-war camps after World War II. 12 In these patients, other symptoms included sensorineural deafness, dizziness, confusion, spastic leg weakness, foot drop, Wernicke's encephalopathy, and rare cases of neck...

Subarachnoid Hemorrhage SAH

SAH is a common and often devastating condition. Despite considerable advances in diagnostic, surgical, and anesthetic techniques and perioperative management, the outcome for patients with SAH remains poor. Pathogenesis and Pathophysiology. SAH is most often caused by leakage of blood from abnormal blood vessels on the surface of the brain resulting in aneurysms and vascular malformations. Aneurysms, often referred to as berry or congenital, are outpouchings on arteries probably caused by a...

Methyl Alcohol

Methyl alcohol (methanol, wood alcohol) is used as a solvent, a component of antifreeze, and an adulterant of alcoholic beverages. While this chemical is only mildly toxic, it is oxidized to formaldehyde and formic acid, which produce severe acidosis and are responsible for the symptoms of methanol abuse. Neuropathological changes in the form of shrinkages and degeneration of neurons, primarily in the parietal cortex, have been reported. y The oxidation and excretion of methyl alcohol is so...

Associated Neurological Findings

Dysphagia and changes in speech similar to that which is produced by a lesion of the cranial nerves or their nuclei may occur with interruption of the corticobulbar fibers, which provide the brain stem nuclei with innervation from the frontal cerebral cortex. This condition is referred to as pseudobulbar palsy. The brain stem nuclei receive bilateral input consequently, a unilateral lesion does not result in bulbar symptoms. Speech and swallowing disorders are due to bilateral injury...

Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS), which is also called motor neuron disease, Charcot's disease, or Lou Gehrig's disease, is an age-dependent fatal paralytic disorder caused by the degeneration of motor neurons in the motor cortex, brain stem, and spinal cord. About 10 percent of cases are familial (FALS) and the rest are sporadic (SALS). Pathogenesis and Pathophysiology. ALS is a combined gray and white matter disease, affecting motor cells and motor fiber tracts. The hallmark of ALS is...

Botulism

Botulism is the most potent poison known to man. It is produced by the spores of C ostridium botu inum. Three distinct varieties of the disease exist. Foodborne botulism results primarily from the ingestion of contaminated home-canned fruits and vegetables. Since this type of botulinum toxin is produced by spores that are already formed and ingested, toxic signs appear rapidly, usually between 8 and 36 hours after ingestion, and an incubation period is not...

General Management Goals

General pharmacological management of conditions affecting hearing is nearly nonexistent, in spite of many attempts over the years using vasoactive agents, steroids, and agents for allergy. io When a specific etiology is known, _TABLE 12-10 -- ON CAUSES OF CENTRAL VERTIGO_ Stroke and TIA Cerebellum AICA distribution PICA distribution Vertebrobasilar migraine Adult form Childhood variant (benign paroxysmal vertigo of childhood) Seizure (temporal lobe) Multiple sclerosis, postinfectious...

Table 122 Ototoxic Medications

Aspirin and sodium salicylate (cochleotoxic, reversible) Chemotherapy (mainly mixed toxicity) TABLE 12-3 -- CLINICOANATOMICAL CORRELATIONS OF DISORDERS OF CRANIAL NERVE Vlil-AUDITORY SYSTEM TABLE 12-3 -- CLINICOANATOMICAL CORRELATIONS OF DISORDERS OF CRANIAL NERVE Vlil-AUDITORY SYSTEM ossicular chain, ending at the stapes. Sound energy is then converted into changes in neural firing, which is passed more centrally through a complex cross-connected network of neurons. This neural network can be...

Posterior Fossa Anomalies

The development of the brain stem and cerebellum has been extensively investigated at the anatomical, cellular, and molecular levels.y The cerebellum is entirely derived from the rhombic lip, a dorsal ridge of the developing neural tube located at the junction between the midbrain and hindbrain rhombencephalon . Proliferation and migration at the rhombic lip results in caudal growth of the cerebellar anlagen, with the cerebellum forming the roof of the fourth...

Inorganic Mercury

Elemental mercury is transported in blood plasma, proteins, and hemoglobin. In the appropriate conditions, mercury may be incorporated rapidly into the brain. Once incorporated into the body, mercury can be found in the urine as long as 6 years after exposure has ceased. Inorganic mercury has the greatest affinity for the kidney. Although concentrations are lower in the CNS, they may still be significant. In the brain, animal studies have shown that the highest...

Organochlorine Insecticides

The neurotoxic mechanisms for dichlorodiphenyltrichloroethane DDT and other organochlorine insecticides is not well defined but may involve the excessive and spontaneous release of TABLE 39-4 -- SYMPTOMS ASSOCIATED WITH EXPOSURE TO GASES TABLE 39-4 -- SYMPTOMS ASSOCIATED WITH EXPOSURE TO GASES Binds to hemoglobin, creating tissue oxygen deprivation mitochondrial toxin Headaches irntability dizziness cognitive decline impaired vision blindness deafness seizures,...

Vertebrobasilar Stroke Syndromes

The circumferential vessels perfuse the lateral brain stem, and the perforant vessels directly from the large basilar or vertebral arteries perfuse the midline structures. While obstruction of the circumferential arteries gives rise to standard syndromes, there is great variability in the perforant vessels, and therefore several syndromes are described. As a rule, midline syndromes affect the pyramidal system, consciousness, and midline cranial nerves extraocular muscles , whereas lateral...

Carbon Monoxide

Carbon monoxide enters the bloodstream through pulmonary absorption and binds reversibly to hemoglobin. The affinity of hemoglobin for carbon monoxide is about 225 times greater than that for oxygen. Thus, exposure to carbon monoxide resulting in increased carboxyhemoglobin decreases the amount of oxygen carried by the red blood cell. This results in pronounced tissue oxygen deprivation. Pathoclinical correlates generally show globus pallidus lucency and...

Arsenic

Although arsenic is rapidly absorbed through the mucous membranes and the skin, although the most common route is ingestion. Arsenic rapidly leaves the bloodstream for storage in the liver, kidneys, intestines, spleen, lymph nodes, and bones, and within 2 weeks it is deposited in the hair, remaining there for years. It also remains in the bones for extended periods of time. Excretion through the kidneys and feces is slow. A single dose may require up to 10 days...

Neuroimaging

CT scan of temporal bone ELECTROPHYSIOLOGY LABORATORY PROCEDURES FOR DISORDERS RELATED TO THE EIGHTH NERVE Indication Central vertigo or hearing loss abnormal BAER TIA or CVA Suspect fistula, cholesteatoma, mastoiditis, congenital abnormality Otoacoustic emissions VESTIBULAR TESTING ENG Fistula test Posturography OTHER TESTS Ambulatory event monitoring Holter monitoring Tilt table testing Post-traumatic vertigo Vertigo with disturbed consciousness Asymmetrical hearing loss Central hearing...