Developmental Disorders
Abstract
Developmental disorders of the central nervous system originate during fetal development. These disorders may cause neurologic symptoms that manifest when the individual is an adult and may result in cognitive impairment, sensory/motor deficits, and pain. Treatment may include observation, medical, or surgical intervention. Understanding the symptoms of developmental disorders along with their treatment and associated complications will enhance the level of care that the health care team can provide to these patients and the support they can offer to the patient’s family during treatment and rehabilitation.
Keywords: arachnoid cyst, chiari malformation, encephalocele, myelomeningocele, syrinx, tethered cord
13.1 Developmental Disorders
Most developmental disorders are present at birth and are therefore diagnosed in patients when they are newborns or young children. Children with developmental disorders may still be affected by these disorders in adulthood; in other cases, disorders do not become symptomatic until a person reaches adulthood. Hydrocephalus may be a developmental disorder, or it may be acquired through other central nervous system (CNS) disorders, such as tumor, trauma, or stroke. Because of its importance in neurologic nursing, hydrocephalus is discussed in its own chapter, Chapter 4: Hydrocephalus. The present chapter addresses other developmental disorders that may be encountered in adult patients.
13.2 Arachnoid Cysts
Primary arachnoid cysts are congenital lesions that arise during embryonic development, typically in the middle cranial fossa. These sacs, which are filled with cerebrospinal fluid (CSF), are located between the brain or spinal cord and the arachnoid membrane. Although they may be large, they do not always cause symptoms (▶ Fig. 13.1).
Form when the arachnoid membranes split during development
Usually capable of secreting CSF
Some contain other types of tissue, such as glial or ependymal cells
Secondary arachnoid cysts are uncommon but may result from head injury, meningitis, tumor, or brain surgery.
Fig. 13.1 Arachnoid cyst on magnetic resonance imaging.
13.2.1 Epidemiology of Arachnoid Cysts
Incidence of 5 per 1,000 in autopsy studies
Male predominance (4:1 ratio)
Primary type typically occurs before age 20 years, especially during the first year of life
13.2.2 Clinical Manifestations of Arachnoid Cysts
Symptoms depend on the size and location of the cyst
Common symptoms include headache, nausea, and seizures; some patients are asymptomatic
Decreased level of consciousness is possible
May include symptoms of hydrocephalus (e.g., headache, nausea, sleepiness, blurred vision, irritability)
13.2.3 Diagnosis of Arachnoid Cysts
Patient’s medical history
Imaging studies
Computed tomography (CT)
Magnetic resonance imaging (MRI)
13.2.4 Treatment of Arachnoid Cysts
Medical Treatment
Observation for small cysts with no symptoms or minor symptoms
Symptom relief (e.g., analgesics for pain)
Surgical Treatment
Cyst fenestration (i.e., perforation) is the preferred treatment
Resection via minimally invasive surgery to remove or open cyst membrane to drain CSF
Shunt for hydrocephalus (used less frequently today than in the past)
Complications of Treatment
Shunt failure
Cyst reaccumulation
13.3 Chiari Malformations
Chiari malformations, sometimes called Arnold-Chiari malformations, occur when the cerebellum and medulla oblongata breach the foramen magnum and invade the spinal column. There are three types of Chiari malformation abnormalities. Types I and II are the most common, and type III is severe and is associated with a very poor prognosis. Because of its rarity, type III is not discussed in this chapter.
13.3.1 Type I Chiari Malformation
In patients with a type I Chiari malformation, the cerebellar tonsils are displaced downward below the level of the foramen magnum, without displacement of the medulla (▶ Fig. 13.2). The condition may develop when the bony space holding the cerebellum is smaller than normal, which pushes the cerebellum and brainstem downward. This displacement puts pressure on the cerebellum, which impedes CSF flow. The condition is often an incidental finding during work-up for another condition.
Fig. 13.2 Type I Chiari malformation.
Epidemiology of Type I Chiari Malformation
Average age at presentation is about 40 years
Slight female preponderance
May be associated with posterior fossa arachnoid cyst
Clinical Manifestations of Type I Chiari Malformation
Affected persons are usually asymptomatic
Common symptoms are wide-ranging but may include the following:
Headache at back of the head aggravated by coughing
Motor/sensory changes
Dizziness or ataxia
13.3.2 Type II Chiari Malformation
The type II Chiari malformation is an abnormality in which the cerebellar tonsils and brainstem are displaced downward below the level of the foramen magnum. Type II Chiari malformations are usually associated with a myelomeningocele and spina bifida (▶ Fig. 13.3).
Fig. 13.3 Type II Chiari malformation.
Epidemiology of Type II Chiari Malformation
Most common in children
Clinical Manifestations of Type II Chiari Malformation
Symptoms of brainstem compression
Cranial nerve dysfunction, especially of the lower cranial nerves
Periods of apnea
Hydrocephalus is common (from obstruction of the fourth ventricle)
Diagnosis of Type II Chiari Malformation
Patient’s medical history
Imaging studies
CT
MRI
Treatment of Type II Chiari Malformation
Medical Treatment
Observation in early stages
Symptom control (e.g., analgesics for pain)
Surgical Treatment
Placement of a shunt for hydrocephalus
Decompression of Chiari malformation in symptomatic patients
13.4 Encephalocele
An encephalocele is a rare type of neural tube defect that may be present before or after birth. It results from failure of the neural tube to close during fetal development and involves the herniation of intracranial contents—usually meninges and brain tissue—through a defect in the skull. Most cases are diagnosed in infants immediately after birth and are associated with other deformities, but some may present later in life.
13.4.1 Clinical Manifestations of Encephalocele
The clinical manifestations of encephalocele depend on the location and size of the abnormality. An encephalocele may resemble a cyst on a prenatal ultrasound examination. Small encephaloceles (e.g., near the sinuses or nose, or on the forehead) may not be noticed immediately after birth. Encephaloceles may be associated with developmental delays and neurologic deficits.
13.4.2 Diagnosis of Encephalocele
Patient’s medical history
Clinical assessment
Imaging studies
CT
MRI
13.4.3 Treatment of Encephalocele
Surgical intervention is usually necessary, but a thin layer of skin covering the encephalocele can allow delay of surgery for a few months.
Observation if surgery is not needed immediately
Surgery if patient is symptomatic
13.5 Other Developmental Disorders
13.5.1 Syrinx
A syrinx is a long, fluid-filled cyst located within the spinal cord that occurs most commonly during fetal development, but it can also result from trauma, meningitis, hemorrhage, tumor, or arachnoiditis (▶ Fig. 13.4). It expands over time, damaging the spinal cord and resulting in a condition known as syringomyelia.
Associated with Chiari malformations, as well as other conditions (Box 13.1 Conditions Associated with Syrinx)
Headaches and motor/sensory deficits are the most common symptoms
Diagnosed by MRI
Most common at cervical level
Treated by surgical decompression
If left untreated, a syrinx can progress to weakness in extremities, loss of sensation in hands, and severe chronic pain.
Fig. 13.4 Syrinx.
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