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Paediatric oculomotor nerve palsies are rare lesions. The most frequently cited mechanism is perinatal injury to the peripheral third nerve,1 although they may be due to congenital absence of the nerve and/or nucleus and be accompanied by neurological deficits.2–4 Septo-optic dysplasia consists of optic hypoplasia, mid-brain malformations, and hypothalamohypophyseal dysfunction. We present three children with congenital third nerve palsy and septo-optic dysplasia.
We report on three children with bilateral optic nerve hypoplasia, with visual function from light projection to 0.05 and nystagmus. Magnetic resonance imaging revealed absent septum pellucidum, thinning of corpus callosum, and posterior pituitary ectopia in two cases and infundibular hypoplasia in the third case. They had anterior pituitary hormone deficiency—growth hormone, adrenocorticotrophic hormone, and hypothyroidism in case one and two, with additional diabetes insipidus in the third case. There were no other associated brain or ocular anomalies. These children had no positive history of perinatal trauma, drugs, or toxic agents. There was no history of parental consanguinity.
Case 1: unilateral, left, pupil sparing third nerve palsy, with fixed exodeviation of 45 prism dioptres and hypotropia of 30 prism dioptres, no aberrant regeneration, no ptosis.
Case 2: fixing with the paretic left eye (visual acuity 0.05 both eyes) demonstrated an elevation deficit of −3, adduction deficit of −2 on this side but good depression. There was no ptosis, anisocoria, or aberrant regeneration of the oculomotor nerve.
The third case was brought to our attention immediately after birth with bilateral third nerve palsy and pupil involvement on the left side (figs 1 and 2). Orthoptic examination revealed bilateral defective medial gaze and elevation and defective depression on the left side. In course of the first year of life pupillary reaction recovered without aberrant regeneration. At the age of 12 years the child died during febrile illness.
Our three children with septo-optic dysplasia had unilateral congenital third nerve palsy in two cases and bilateral palsy in one case. There was no ptosis and no involvement of the contralateral superior rectus muscle in the two patients with unilateral nerve disturbance, indicative perhaps of peripheral nerve defect. A possible explanation for the lack of aberrant regeneration may be due to extreme atrophy or even absence of the third nerve.5 The child with bilateral third nerve palsy (case 3) had postnatal pupillary involvement in one eye, with regeneration within 1 year. Peripheral nerve damage as well as nuclear defects may have been responsible. Previous reports in the literature showed that several kinds of brain damage could result in congenital oculomotor palsies, such as brainstem infarction, cerebellar and midbrain hypoplasia, absence of basal ganglia, etc.5,6
Two theories have been proposed regarding the pathogenesis of septo-optic dysplasia. As all affected components arise from different tissues and processes at different times developmental anomaly or dysplasia makes little embryological sense. Genetic causes are exceptional.7 A vascular disruptive sequence similar to porencephaly, possibly involving the proximal trunk of the anterior cerebral artery is discussed by Lubinsky.8 Our findings of congenital third nerve palsy in de Morsier syndrome do not support this hypothesis, as the third cranial nerve and its nuclei are not within the territorial distribution of the anterior cerebral artery and there were no additional defects in the median and paramedian areas of the frontal lobes. The partial palsy in case two, with some amount of adduction, elevation, and depression and the recovery of the pupillary involvement in case three implicate probably prenatal traumatic, infectious or toxic insults, thus supporting the theory of secondary degeneration.
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