Chapter 83 Cranial nerve and eye muscle palsies
Apart from congenital IVth nerve palsy, childhood congenital and acquired infranuclear ocular motor palsies are uncommon. Because of this and concerns about the potential serious underlying pathology, these cases are usually referred to specialist centers. However, the principles of history taking, examination, diagnosis, and documentation are the same as those applied to more routine ocular motility cases. All ophthalmologists whose practices include child referrals should be familiar with the investigation and management of these cases and establish a network of contacts with pediatric neurology and neuroimaging colleagues to optimize outcomes.
A. Congenital cranial dysinnervation disorder (CCDD) (see Chapter 82). This is the commonest cause of bilateral congenital IIIrd nerve palsy. Inherited genetic mutations lead to primary maldevelopment of either the IIIrd (CFEOM1) or the IIIrd and IVth cranial nerve nuclei (CFEOM2). Clinical features include bilateral ptosis and symmetrically reduced elevation and adduction. High resolution MRI shows cranial nerve hypoplasia.1
A. Clinical features suggesting pre- or perinatal peripheral IIIrd nerve damage, viz. variable IIIrd nerve innervated muscle involvement and signs of misdirection regeneration. The palsy may be isolated or associated with additional perinatal neurologic damage (Fig. 83.1).2
B. With features suggesting a primary nuclear maldevelopment, viz. bilateral partial ptosis and contralateral superior rectus palsy. A hypoplastic peripheral IIIrd nerve may be seen on MR imaging and specific genetic mutations known to be associated with CCDD identified.
Whether or not it will be possible to successfully align the affected eye with strabismus surgery will depend on the extent of the palsy. The outcome in a complete IIIrd nerve palsy is likely to be disappointing. The eye position should be corrected first before considering ptosis surgery. Ptosis surgery should not be undertaken unless corneal protection can be guaranteed.
The commonest cause is accidental closed head injury, e.g. in a road traffic accident. Isolated IIIrd nerve palsy is due to avulsion of the nerve rootlets from the brain stem. With basal skull fracture there are likely to be multiple cranial neuropathies.
IIIrd nerve palsy occurring after minor head trauma may indicate an underlying predisposing factor. IIIrd nerve palsy has been described after non-accidental injury in infants and following surgical trauma. Some spontaneous recovery for up to a year can be expected, often with misdirection–regeneration.
A. Bacterial meningitis. In neonates, due to group B streptococcal infection (also Escherichia coli/listeria with brain stem encephalitis), it may be complicated by unilateral or bilateral IIIrd; recovery is likely to be poor. Cerebral visual impairment is also common (see Chapter 56). IIIrd nerve palsy can also occur in infantile or childhood meningitis.
C. Para-infectious palsy. A presumed immune-mediated pathology is responsible for cases described after, for example, influenza vaccination or MMR (measles, mumps, rubella) vaccination. The condition can be recurrent.
Intracranial and intraorbital tumors can present with signs including a IIIrd nerve palsy, usually progressively worsening (Fig. 83.3). External compression, direct involvement of the nerve (e.g. by schwannoma), infiltration, or malignant meningitis may be responsible. Compression can be anywhere along the course of the nerve (e.g. brainstem glioma or parasellar tumor). Raised intracranial pressure may be a contributory or primary cause.
A. Aneurysmal compression. This may occur in the first or second decade due to posterior communicating artery aneurysm: also (usually with a VIth nerve palsy) due to intracavernous internal carotid artery aneurysm in, for example, Loewys-Dietz syndrome (Fig. 83.4).
This is a diagnosis of exclusion after full investigation.3 It cannot be made on clinical grounds alone. The syndrome is not certainly due to migraine. The diagnostic criteria are:
• Neuroimaging normal except for enlargement and gadolinium enhancement of the cisternal portion of the IIIrd nerve on MRI (not invariable).4 The cerebrospinal fluid (CSF) is normal.
Fig. 83.5 Recurrent right IIIrd nerve palsy × 3 from ages 5 to 9. Axial T1-weighted FS post gadolinium shows enhancing nodule on right IIIrd nerve. The scan also shows bilateral vestibular schwannomas indicating NF2.
Despite full investigation, a small proportion of childhood onset IIIrd nerve palsies remain unexplained. It is important to be prepared to reinvestigate if new signs develop; ocular myasthenia, for example, can present as a unilateral pupil sparing IIIrd nerve palsy with negative antibodies and normal electromyography.6
At least 1 year from onset (e.g. of a traumatic palsy) should be allowed for spontaneous recovery before considering surgical treatment. Attempts to correct a neurogenic hypotropia by inferior rectus recession always lead to an abnormal recessed lower lid position: a better option is to move both horizontal muscles upwards with augmenting sutures if necessary.
• An abnormal head posture (AHP) – possibly detectable from early infancy onwards. This consists of a tilt and turn of the head away from the side of the lesion (for differential diagnosis, see Box 83.1).8
• Without the AHP, a hypertropia of the affected eye which increases in adduction and reduces in abduction. This is associated with ipsilateral inferior oblique overaction/superior oblique underaction and contralateral superior rectus underaction/inferior rectus overaction.
Differential diagnosis of a head tilt/turn in childhood