Color Atlas of Neurology

Subacute and Chronic Myelopathies

Spinal cord syndromes (p. 282) may be subacute or chronic depending on their cause. The

! Mass Lesions

complete clinical picture may develop over days to weeks (subacute) or months to years (chronic). For myelopathies due to developmental disorders, see p. 288ff.

Causes

Spinal cord compression2 by cervical spine lesions3

Diagnosis/Treatment1

MRI, CT, myelography; evoked potentials, EMG for radicular lesions, plain radiograph of cervical spine.

Treatment: Surgery for progressive impairment or severe stenosis; otherwise, symptomatic treatment

Extramedullary,

intradural/ leptomeningeal

Extradural

Calcified

vessel

Intervertebral disk

Narrowing of lumbar spinal canal, spondylarthrosis

Spinal claudication

Vascular lesion of spinal cord

Extradural compression (vertebral body metastasis)

Dura

Leptomeninx

Intramedullary

Leptomeningeal, radicular

Radicular

! Non-Mass Lesions

Myelitis. See p. 282 for a listing of various infectious myelitides.

Subacute combined degeneration (SCD) appears in middle to old age, causing tingling and burning dysesthesiae in the limbs, gait unsteadiness, and abnormal fatigability. There may also be visual disturbances and depressive or psychotic symptoms accompanied by weight loss, glossopyrosis, and abdominal complaints. The neurological examination reveals a loss of position sensation ( spinal ataxia), spastic paraparesis, variable abnormalities of the deep tendon reflexes, and autonomic dysfunction (bladder, bowel, sexual dysfunction). Megalocytic anemia is usually present. The cause is vitamin B12 deficiency, which may, in turn, be due to malabsorption, cachexia, or various medications. Folic acid deficiency produces a similar syndrome. The patient should be treated with parenteral cyanocobalamin or hydroxocobalamin as soon as possible. Neurological deficits can arise even if

Diagnostic Studies in Myelopathy1

the hematocrit and red blood cell count are normal.

Toxic myelopathy. Most patients initially present with polyneuropathy, developing clinically apparent myelopathy only in the later stages of disease. Common causes include solvent abuse (“glue sniffing”), a high dietary intake of gross peas (lathyrism; p. 304), and consumption of cooking oil adulterated with lubricant oil (triorthocresyl phosphate poisoning).

Hereditary. The clinically and genetically heterogeneous forms of familial spastic paraplegia (FSP; spinal paralysis = SPG, p. 384) become symptomatic either in the first decade of life or between the ages of 10 and 40. Progressive central paraparesis with spasticity arises either in isolation (uncomplicated SPG) or accompanied by variable neurological deficits (complicated SPG). Both types can be transmitted in an autosomal dominant, autosomal recessive, or X- linked inheritance pattern. Spinal muscular atrophy, see p. 304. Adrenomyeloneuropathy, see p. 384.

Hereditary Diseases

Phenotype. The manner in which a hereditary disease expresses itself at a given moment in development (phenotype) is the product of both the individual’s genetic makeup (genotype) and the environment in which development has taken place.

Inheritance. The human genome consists of 22 pairs of chromosomes (autosomes) and 2 sex chromosomes (either XX or XY). Individuals inherithalfoftheirchromosomesfromeachparent. The chromosomes are made of DNA and bear the genes,sequencesofnucleotidebasepairsthatencode the proteins of the body. Stretches of DNA that encode proteins are called exons; there are also intervening noncoding sequences, called introns. The inheritance pattern of hereditary diseases can be monogenic—the disease is due to a defect in a single (autosomal or X-chromosomal) gene, and is transmitted in a recessive or dominant manner in accordance with Mendel’s laws; polygenic—the disease is due to defects in multiple genes; or multifactorial—the cause of disease is not exclusively genetic, and exogenous factors along with genetic factors determine its phenotype. Mitochondrial disorders are transmitted exclusively by maternal inheritance, as mitochondrial DNA is nonchromosomal and is inherited exclusively from the mother.

Mutation. Alleles are different forms of a gene. A gene mutation is a change in the DNA sequence of a gene and may involve a change in a single base pair(pointmutation),thelossofoneormorebase pairs (deletion), the insertion of one or more base pairs, or unstable trinucleotide repeats. There are also genome mutations, which involve a change in the number of chromosomes, such as trisomy 21 (thecauseofDownsyndrome),aswellas chromosome mutations, in which the chromosomal structure is altered. Mutations can occur either in the germ cells (germ-line mutation) or in the differentiated cells of the body (somatic mutation). Somatic mutations cause cancer, autoimmune diseases, and congenital anomalies.

Diagnosis. The diagnosis of hereditary diseases is by family history. Many monogenic diseases can be diagnosed by direct genotypic analysis (DNA sequencing). Indirect genotypic analysis, with investigationoftheaffectedandnonaffectedmembers of a single pedigree, is used in the diagnosis of disorders for which a gene locus is known but the responsible mutation(s) has not yet been determined.

Malformations and Developmental

Anomalies (Table 40, p. 381)

Malformation. A malformation is a structural abnormality of an organ or part of the body in an individual whose body tissues are otherwise normal. Malformations arise during prenatal development because of primary absence or abnormality of the primordial tissue destined to develop into a particular part of the body (“anlage”). Dysplasia is malformation due to anomalous organization or function of tissues and tissue components; disorders involving dysplasia include tuberous sclerosis, neurofibromatosis, migration disorders, and various neoplastic diseases.

Developmental anomaly. Disruption of the growthofanorganorbodypartafternormal(primary) primordial development can cause a secondary developmental anomaly. Mechanical influences during development can cause an anomalous position and shape (deformity) of an organ or body part.

! Infantile Cerebral Palsy (CP) (p. 291)

Infantile cerebral palsy (cerebral movement disorder) is a manifest, but not necessarily unvarying, motor and postural disorder caused by nonprogressivedamagetothebrainbefore,during,or after birth. The underlying brain damage is usually of multifactorial origin. Prenatal causes include chromosomal defects, infection, hypoxia, or blood group intolerance; perinatal causes include hypoxia, cerebral hemorrhage, birth injury, adverse drug effects, and kernicterus; postnatal causes include meningoencephalitis, stroke, brain tumor, metabolic disturbances, and trauma.

Symptoms and signs. Paucity of spontaneous movement, abnormal patterns of movement, and delayed development of standing and walking are noted just after birth and as the child develops. Cerebral palsy frequently involves central paresis (hemiparesis, paraparesis, or quadriparesis), spasticity, ataxia, and choreoathetosis (p. 66). There may also be mental retardation, epileptic seizures, behavioral disturbances (restlessness, impulsiveness, lack of concentration, impaired affect control), and impairment of vision, hearing, and speech. The motor disturbances produce deformities of the bones and joints (talipes equinus, contracture, scoliosis, hip dislocation).

Hydrocephalus

Postural abnormalities, spasticity

Porencephaly

Lateral ventricle (anterior horn)

Choreoathetosis

Adduction position, skeletal deformity

Arachnoid cyst

Abnormal posture of foot

CT scan (axial view)

MRI scan (coronal T1-weighted )