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The underlying pathology of congenital oculomotor nerve palsy has not been determined. A previous MRI study reported that only one out of three patients showed bilateral oculomotor nerve hypoplasia; the two remaining patients had subarachnoid oculomotor nerves of normal size.1 This variability suggests heterogeneity in the pathogenesis of congenital oculomotor nerve palsy. This report describes the use of MRI to verify the pathology of the extraocular muscles as well as the cranial nerves in three patients with congenital oculomotor nerve palsy. This study was undertaken following the tenets of the Declaration of Helsinki and received an approval from Institutional Review Board of Seoul National University Bundang Hospital.
A 6-month-old girl presented with an inability to elevate the right eye. There was an intermittent exotropia of 20 dioptres (PD). Ductions and versions showed underaction of elevation, depression and adduction OD (fig 1A). MRI showed normal right and left oculomotor nerves and slightly atrophic right inferior rectus (fig 1B,C).
An 8-year-old boy presented with the inability to elevate his right eye, present since early childhood. He had a very small ptosis in the right eye with a marginal reflect distance 1 of −1 OD and +1.5 OS. Levator function was 7 mm OD and 12 mm OS. There was a right exotropia of 25 PD and a hypotropia of 6 PD. Ductions and versions showed a severe underaction of elevation and a mild to moderate underaction of depression and adduction OD (fig 1D). MRI showed normal right and left oculomotor nerves and moderately atrophic right superior, medial and inferior rectus muscles (fig 1E,F).
A 41-year-old woman presented with a life long, constant residual exotropia without diplopia. There was a left exotropia of 16 PD and a left hypotropia of 8 PD. Ductions and versions showed a severe underaction of elevation and moderate underaction of depression and adduction OD (fig 2A). MRI showed absent right oculomotor nerve and markedly atrophic right medial and inferior rectus muscles (fig 2B,C).
Our study first showed atrophy of the extraocular muscles, which was more remarkable with increased age in patients with congenital oculomotor nerve palsy. The degree of atrophy of the superior, medial and inferior recti in the three patients appeared to increase with age. However, the number of patients studied was too small to reach any conclusions.
Congenital cranial dysinnervation disorders (CCDDs) represent developmental abnormalities that include the complete absence of the cranial nerves with primary or secondary muscle dysinnervation.2 In addition, aplasia or hypoplasia of the oculomotor or abducens nerve has been reported with MR imaging of patients with congenital oculomotor nerve palsy,1 3 as well as Duane retraction syndrome4 and congenital fibrosis syndromes.1 4 5 6 In the previous reports on congenital oculomotor nerve palsy, the MR imaging findings varied from aplasia, hypoplasia to normal.1 3 However, the previous study did not provide any detailed information about the patients, nor any photographs to show the ocular movement. Therefore, further imaging studies are required to fully describe the imaging findings associated with congenital oculomotor nerve palsy. In our study of three patients with congenital oculomotor nerve palsy, only one out of the three patients had ipsilateral aplasia of the oculomotor nerve on MRI; the two other patients had no oculomotor nerve abnormalities. Therefore, CCDDs can only partially explain the underlying cause of congenital oculomotor nerve palsy.
In conclusion, the results of this study suggest that CCDDs as a manifestation of congenital aplasia or hypoplasia appear to only partially explain the underlying cause of oculomotor nerve palsy.
Funding This study was supported by a grant no R01-2005-000-10875-0 from the Basic Research Program of the Korea Science & Engineering Foundation.
Competing interests None.
Provenance and Peer review Not commissioned; externally peer reviewed.
Ethics approval Ethics approval was provided by Seoul National University Bundang Hospital.
Patient consent Obtained from the parents and patient.
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