Abnormal Optic Nerve

The Problem

The optic nerve is abnormal

Common Causes

Optic nerve hypoplasia

Papilledema

Optic nerve coloboma

Glaucoma

Other Causes

Pseudopapilledema

Myelinated nerve fibers

Albinism

KEY FINDINGS

History

Optic nerve hypoplasia

If bilateral, often presents with poor vision and abnormal eye movements in infancy

Unilateral hypoplasia may be associated with strabismus due to decreased vision

If pituitary dysfunction, may have poor growth, developmental delay, and abnormal stress response

Papilledema

Headache Double vision

Transient visual obscuration (brief episodes of dimmed vision)

Idiopathic intracranial hypertension

Frequently associated with medication in children Corticosteroids, retinoic acid

Also associated with obesity Optic nerve coloboma

Abnormal pupil appearance (if iris coloboma present) Poor vision or strabismus if fovea affected

Associated systemic diseases CHARGE Association

Glaucoma

May have family history Infants and young children

Light sensitivity

Eye appears large, cornea cloudy Older children

Usually asymptomatic Pseudopapilledema

Optic disc drusen Trisomy 21 Farsightedness

Myelinated nerve fibers Decreased vision due to myopia

Examination

Optic nerve hypoplasia

Infant with poor vision, nystagmus Poor pupil responses

Papilledema

Visual acuity usually normal (unless severe) Optic nerve elevated, swollen, hemorrhages,

cotton wool spots

Decreased outward movement of eye due to sixth nerve palsy

Optic nerve coloboma

May have associated iris coloboma Variable involvement of optic nerve, retina Usually inferonasal quadrant

Glaucoma

Infants and young children

Corneal clouding, eye larger than normal Usually unable to visualize optic nerve

Older children

Enlarged cup:disc ratio Pseudopapilledema

Trisomy 21—abnormal vascular pattern Optic nerve drusen

Irregular lumpy appearance White deposits within nerve

Myelinated nerve fibers

White feathery appearance beginning at optic nerve

Extend along course of retinal nerve fibers

124 ■ Section 2: Symptoms

WHAT SHOULD YOU DO?

Similar to examination for retinal hemorrhages, evaluation of the optic nerve is often difficult in pediatric patients, particularly infants and toddlers. In older children, examination of the nerve may be part of the routine well-child examination, or may be performed due to specific symptoms (such as headache). The presence of papilledema requires prompt evaluation, including neuroimaging and consultation with a neurologist. If the patient has an abnormal-appearing nerve, but no symptoms of increased intracranial pressure, referral to a pediatric ophthalmologist should be considered to evaluate for pseudopapilledema, which could obviate the need for further extensive testing. Most children with other abnormal optic nerve findings should be referred to a pediatric ophthalmologist.

What Shouldn’t Be Missed

Optic nerve hypoplasia is a frequent cause of very poor vision and nystagmus in infants. Due to the difficulty of direct ophthalmoscopic evaluation of the optic nerves in infants with nystagmus, such patients require referral to a pediatric ophthalmologist. Optic nerve hypoplasia may be associated with pituitary abnormalities, and these patients may be unable to mount a normal stress response, potentially causing severe problems during even mild illnesses. This possibility should be kept in mind until the patient is evaluated by an endocrinologist.

Papilledema may occur in patients with idiopathic intracranial hypertension. In children, this is most commonly associated with medication use, such as corticosteroids or retinoic acid. Prompt evaluation is indicated to rule out intracranial tumors or other abnormalities and minimize the risk of vision loss associated with untreated papilledema.

COMMON CAUSES

1.Optic nerve hypoplasia. Optic nerve hypoplasia is a common cause of decreased vision in infants (Figure 21–1). This diagnosis usually cannot be made by the pediatrician due to the difficulty examining the optic nerves in infants with nystagmus. However, this potential diagnosis should be kept in mind while the evaluation is in progress, due to the risk of associated pituitary problems.

2.Papilledema. True papilledema usually results from increased intracranial pressure (Figure 21–2). This may occur due to space-occupying

A

B

FIGURE 21–1 ■ Unilateral optic nerve hypoplasia. (A) The edge of the nerve is marked by an arrow. The surrounding depigmented area gives the “double ring sign.” (B) The other optic nerve is normal.

FIGURE 21–2 ■ Marked papilledema in a patient with idiopathic intracranial hypertension. Note obscuration of disc margin, cotton wool spots (arrow), and multiple splinter hemorrhages.

Table 21–1.

Causes of Papilledema

■Increased intracranial pressure

Intracranial mass lesion

Trauma

Idiopathic intracranial hypertension

■Orbital lesion

■Some optic neuritis

lesions, trauma, or idiopathic intracranial hypertension (pseudotumor cerebri) (Table 21–1). It may also arise due to tumors within the optic nerve (Figure 21–3A and B). The finding of papilledema warrants prompt evaluation.

3.Optic nerve coloboma. Optic nerve colobomas result from incomplete closure during the

A

B

FIGURE 21–3 ■ Papilledema secondary to optic pathway glioma in a patient with neurofibromatosis. (A) Swollen optic nerve head with dilation of retinal vessels and splinter hemorrhages. (B) Magnetic resonance image showing bilateral large optic pathway gliomas.

CHAPTER 21 Abnormal Optic Nerve ■ 125

FIGURE 21–4 ■ Optic nerve coloboma in a patient with CHARGE association.

embryonic development of the eye (Figure 21–4). They are widely variable, both in appearance and in visual consequences.

4.Glaucoma. In infants and young children with glaucoma, the initial signs and symptoms include enlargement of the eye, corneal clouding, and light sensitivity. In older children and adults, the eye does not grow in response to increased intraocular pressure. The pressure causes damage to the optic nerve, producing an increase in the cup:disc ratio (Figure 21–5A and B). The vision loss affects the peripheral visual field first, with gradual constriction until the central vision is affected. Therefore, patients may have substantial loss of vision before the problem is detected. This is why glaucoma is sometimes called “the sneak thief of sight.” This type of minimally symptomatic glaucomatous visual loss is much more common in adults (particularly the elderly) than in children.

5.Pseudopapilledema. The term pseudopapilledema describes patients who have an abnormality of the nerve with an appearance suggesting possible increased intracranial pressure (Table 21–2). Common causes include optic disc drusen (Figure 21–6) and Trisomy 21 (Figure 21–7). It is important to differentiate this abnormality from true papilledema, in order to avoid unnecessary testing.

6.Myelinated nerve fibers. This abnormality has a very distinctive appearance, with white, feathery opacities adjacent to the optic nerve (Figure 21–8). The myelinated nerve fibers themselves do not cause vision problems, but they are frequently associated with asymmetric myopia, which may cause amblyopia.

126 ■ Section 2: Symptoms

A

B

FIGURE 21–5 ■ Unilateral glaucoma. (A) Normal left optic nerve, with cup:disc ratio of approximately 0.3. (B) Right optic nerve with glaucomatous damage (cup:disc ratio of approximately 0.8).

APPROACH TO THE PATIENT

Unlike most of the other chapters in this section, the presence of an abnormal optic nerve is not something that patients or parents will report. However, optic nerve abnormalities may cause other problems that prompt evaluation of the nerve.

FIGURE 21–6 ■ Pseudopapilledema due to optic disc drusen. Note the abnormal branching pattern of the optic disc vessels, and that there is no obscuration of fine vessels as they cross over the nerve.

FIGURE 21–7 ■ Pseudopapilledema in a patient with Trisomy 21. Note the absence of an optic cup and the abnormal branching pattern of the optic nerve vessels.

Table 21–2.

Causes of Pseudopapilledema

■Optic disc drusen

■Trisomy 21

■Marked farsightedness

■Myelinated nerve fibers

FIGURE 21–8 ■ Myelinated nerve fibers, right eye. Striking appearance of white, feathery-bordered opacity adjacent to the optic nerve. The optic nerve itself is normal.

History

The presence of optic nerve abnormalities may be detected during a regular well-child examination, or the optic nerve may be examined due to specific complaints (such as headache). If the child has no complaints, normal vision, and is incidentally found to have an abnormal optic nerve, then there is a good likelihood that this represents pseudopapilledema. However, specific questions should be asked regarding symptoms of increased intracranial pressure.

Optic nerve hypoplasia is in the differential diagnosis of infants with poor vision and nystagmus. Although it may be isolated, it is frequently a manifestation of septo-optic dysplasia. Affected children may have associated central nervous system and pituitary abnormalities, including developmental delay, seizures, and poor growth. An inability to mount a normal stress response due to adrenocorticotropic hormone deficiency may cause the child to have serious systemic problems precipitated by relatively minor illnesses.

If papilledema is suspected based on the child’s complaints or is found on examination, specific questions should be asked. Headaches with nausea and vomiting may be caused by increased intracranial pressure. Horizontal diplopia may occur due to sixth cranial nerve palsy. A frequent symptom in patients with idiopathic intracranial hypertension is transient visual obscurations. These are brief (typically a few seconds) episodes in which the vision becomes dim or blacks out. Idiopathic intracranial hypertension in children is frequently due to medication, particularly retinoic acid and corticosteroids. If a patient with papilledema has been taking these medications, this diagnosis is very likely.

CHAPTER 21 Abnormal Optic Nerve ■ 127

The visual acuity in patients with increased intracranial pressure is usually not affected early in the course of the disease, and therefore normal acuity does not rule out this diagnosis. Evaluation of the optic nerve usually reveals circumferential elevation of the optic nerve head, inability to visualize fine blood vessels as they cross over the surface of the nerve, retinal hemorrhages that are usually feathery and follow the course of the optic nerve fibers, and cotton wool spots.

Patients with pseudopapilledema have a “crowded” appearance of the nerve, and frequently have abnormal branching of the retinal blood vessels over the nerve. Optic disc drusen are a common form of pseudopapilledema in children (Figure 21–6). If they are superficial, white deposits may be visible within the nerve. Myelinated nerve fibers are white, arise just adjacent to the optic nerve, and follow an arcuate pathway along the course of the normal retinal nerve fiber layer (Figure 21–8).

PLAN

Infants with decreased vision and nystagmus should be referred to a pediatric ophthalmologist. The ophthalmological assessment will include evaluation of the optic nerves (Figures 21–9).

Children with true papilledema require prompt evaluation (Figures 21–10). Magnetic resonance imaging is performed initially to rule out a space-occupying lesion or sagittal sinus thrombosis. If the imaging is

Abnormal optic nerve

Examination

Infants with poor vision and nystagmus may have optic nerve hypoplasia, but this cannot be confirmed without indirect ophthalmoscopic examination by a pediatric ophthalmologist. The pediatrician’s examination of such infants will be limited, but the red reflex should be evaluated to look for other causes of decreased vision (e.g., cataracts, retinoblastoma).

Children in whom optic nerve abnormalities are found should have their vision and pupil reactions checked. If a patient has a unilateral problem that affects vision, they may develop sensory strabismus (either esotropia or exotropia). This should be differentiated from esotropia due to a sixth nerve palsy caused by increased intracranial hypertension. The eye can move fully medially and laterally in sensory strabismus, whereas outward movement is limited in sixth cranial nerve palsy.

FIGURE 21–9 ■ Algorithm for evaluation and management of an infant with abnormal optic nerve(s).

normal, referral to a pediatric neurologist for lumbar puncture is indicated to measure intracranial pressure and evaluate the cerebrospinal fluid. Idiopathic intracranial hypertension in children is often due to medication, and discontinuation usually results in rapid improvement.

Children with abnormal-appearing optic nerves who are asymptomatic should be referred to a pediatric ophthalmologist. If pseuopapilledema is confirmed, this may spare the child unnecessary evaluations.

WHAT SHOULDN’T BE MISSED

Although the diagnosis of optic nerve hypoplasia cannot be made without a pediatric ophthalmology examination, this possible diagnosis should be kept in mind while the evaluation of an infant with poor vision and nystagmus is in progress. Some children with septooptic dysplasia have pituitary dysfunction, including

adrenocorticotropic hormone deficiency. These children may be unable to mount a normal stress response and are at risk for decompensation during relatively minor illnesses.

Children with true papilledmea require prompt evaluation to establish a diagnosis and initiate treatment. Early intervention decreases the risk of permanent vision problems.

When to Refer

■Patients with papilledema should be referred promptly for imaging and neurological evaluation

■Patients with optic nerve hypoplasia will usually be referred due to decreased vision and nystagmus in infancy. The diagnosis cannot be established until the nerves are examined by an ophthalmologist.

■Patients with other optic nerve abnormalities found during routine well-child checks should be referred to a pediatric ophthalmologist.