Sarah Pirio Richardson

Seizures and Status Epilepticus

This chapter begins with a discussion that a seizure can have many causes such as metabolic derangements (severe hypoglycemia), infections (encephalitis or from high fever), drugs (amphetamines), drug-withdrawal (alcohol), genetic, or idiopathic. Next, the chapter describes the epidemiology of epilepsy, the pathophysiology of a seizure, and the value of an electroencephalogram in diagnosing seizures. The seizure classification system is then covered and its distinction from non-seizure events such as syncope, migraine, transient ischemic attack, psychogenic nonepileptic seizure, rage attacks, Meniere’s disease attack, and movement disorders. This chapter finishes with a complete description of focal seizures, generalized convulsive seizures (Grand Mal), absence seizures (Petit Mal), West’s syndrome, and status epilepticus. Attention is paid to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of the Spinal Cord and Vertebral Bodies

The spinal cord extends caudally from the medulla to the first or second lumbar vertebrae in adults and slightly lower in infants. Spinal cord functions are not solely passive but also modulate or generate many afferent and efferent pathways. Spinal cord dysfunction results from traumatic, inflammatory, demyelinating, ischemic, nutritional, and degenerative conditions. The chapter begins with a discussion of common major clinical features and mechanisms of damage of the spinal cord. Clinical signs depend on the level of the spinal cord damage and whether the damage involves part or all of the cord. Diseases affecting the spinal cord may present as degenerative with loss of specific spinal cord elements, focal lesions at one or more level of the spinal cord, or compression of spinal cord nerve roots that are exiting the vertebra. Three common diseases of the spinal cord are discussed in detail, amyotrophic lateral sclerosis, acute transverse myelitis, low back pain with radiculopathy or lumbar spinal stenosis, with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of the Cerebrovascular System

The chapter begins with a discussion of common major clinical features and mechanisms of damage to the cerebrovascular system. Stroke is a general term that implies damage to cerebral tissue from insufficient blood to the brain (ischemic stroke or infarction), abnormal excess blood (hemorrhagic stroke or cerebral hemorrhage), or inadequate venous drainage of cerebral blood (venous stroke). Together, these act as the third leading cause of death in the USA. Signs and symptoms produced by strokes depend on which part of the brain is affected and whether the stroke causes increased intracranial pressure. This chapter further discusses the most common types of cerebrovascular disease: transient ischemic attack, ischemic or hemorrhagic stroke, and intracerebral hemorrhages from hypertension, aneurysms, and amyloidosis. Attention is given to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of Peripheral Nerves

The peripheral nervous system involves all nerves lying outside the spinal cord and brainstem except the olfactory and optic nerves that are extensions of the central nervous system itself. All peripheral nerve axons are invested either with a wrapping of myelin made by Schwann cells (myelinated nerve) or by cytoplasm of Schwann cells (unmyelinated nerve). The chapter begins with a discussion of common major clinical features and mechanisms of damage of all motor and sensory nerves. Three common diseases of peripheral nerves are then discussed in detail: diabetic distal symmetrical polyneuropathy, carpal tunnel syndrome, Bell’s palsy or idiopathic peripheral facial nerve palsy, with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of the Brainstem and Cerebellum

The chapter begins with discussion of anatomy and functions of the brainstem (mesencephalon, pons, and medulla) and cerebellum. No other part of the central nervous system is packed with so many critical axon tracts and nuclei. Main brainstem functions are as follows: to provide transit and processing nuclei for ascending and descending pathways that convey signals to and from the cerebellum, cerebrum, and spinal cord; to integrate functions such as consciousness, muscle tone, posture, and normal autonomic functions; and to house cranial nerves 3–10. The cerebellum occupies only 10 % of the brain volume but contains more neurons than the entire rest of the brain. Lesions in the brainstem often manifest as cerebellar, somatosensory and motor symptoms plus cranial nerve dysfunction. Damage to the cerebellum often results in errors in smooth motor movements. The chapter ends with a discussion of central pontine myelinolysis, lateral medullary syndrome or Wallenberg’s syndrome, and spinocerebellar atrophies with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of the Extrapyramidal System

The chapter begins with an overview of human motor system control of both voluntary and involuntary movements. Movement disorders or extrapyramidal disorders are characterized by abnormal movements in conscious patients. Damage to or presumed dysfunction of the basal ganglia and their brainstem and cerebellar connections is implicated in the etiology of these diseases. Movement disorders are characterized by either excessive (hyperkinetic) or reduced (hypokinetic) activity. Hyperkinetic movements are characterized by tremor, chorea, dystonia, athetosis, ballismus, myoclonus, and tics. The reader can view videos of many hyperkinetic movement disorders. The chapter then covers in detail essential tremor, Parkinson’s disease, and Huntington’s disease with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of Muscle

The chapter begins with a discussion of the major types of muscle: skeletal muscle, smooth muscle, and cardiac muscle. Then, it discusses ways to distinguish muscle weakness from other causes of weakness. The chapter focuses on four broad categories of muscle diseases: muscular dystrophy due to genetic abnormalities, channelopathies with abnormal sodium, calcium or potassium membrane ion channels, inflammatory myopathies, and secondary endocrine myopathies. The chapter ends with a complete discussion of four important types of muscle diseases: Duchenne muscular dystrophy, dermatomyositis, statin myotoxicity, and primary hyperkalemic periodic paralysis. For each disease, attention is paid to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of Pain and Headache

The chapter begins with a discussion of the concept of neuropathic and nociceptive pain, its physiology, and its peripheral and central nervous system pathways. The chapter next discusses common major clinical features and mechanisms of damage. The chapter ends with a discussion of tension-type headache, migraine headache, and medication-overuse headache with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of the Vestibular System

The chapter begins with a discussion of the anatomy and physiology of normal balance. The signs, symptoms, and pathophysiology of dizziness, vertigo, and presyncope are then discussed. The chapter ends with a full discussion of benign paroxysmal positional vertigo, vestibular neuritis, and Meniere’s disease or endolymphatic hydrops with attention paid to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.

Disorders of Myelin

The chapter begins with a discussion of common major clinical features and mechanisms of damage to myelin. Myelin is produced in the peripheral nervous system (PNS) by Schwann cells and in the central nervous system (CNS) by oligodendrocytes. Key functions of myelin are to house axons and to provide for the axons hollow tubular channels of extracellular matrix, provide physical strength to the axon, insulate the axon from environmental toxins, and allow saltatory conduction increasing nerve conduction velocity as much as 100-fold. The four major mechanisms of demyelination are death of oligodendrocyte or Schwann cell, interference with myelin synthesis, interference with myelin turnover, and immune-mediated destruction of myelin. In the CNS, myelin tracts commonly damaged are the corticospinal tract (weakness, spasticity), spinothalamic tract (sensory loss), visual pathway (visual disturbance), and spinocerebellar pathways (ataxia). In the PNS, motor (flaccid weakness) and sensory (position sense loss) are often involved. The chapter then discusses multiple sclerosis, neuromyelitis optica, acute disseminated encephalomyelitis, and Guillain–Barre syndrome, with attention to their pathophysiology, major clinical features, major laboratory findings, and principles of management and prognosis.