Abstract
Purpose: :
A relatively new technique in the evaluation of cranial nerves is a high–spatial–resolution MRI with three–dimensional fast imaging employing steady–state acquisition (3–D FIESTA). In this report we assess its usefulness, with focus on an example case of isolated abducens nerve aplasia.
Methods: :
Neuro–imaging was performed using a 1.5–Tesla system. Axial FIESTA sequence was obtained to evaluate the cisternal segments of cranial nerves.
Results: :
An otherwise developmentally normal 12 month old female presented for evaluation of reduced abduction of the left eye, which had been stable since detection at 6 months of age. The child had no similarly affected family members and was a product of a normal pregnancy and uncomplicated spontaneous vaginal delivery. On examination, the only identifiable abnormality was absent abduction of the left eye. Motility was otherwise full and she was orthophoric in primary gaze, without evidence of amblyopia. The patient did not exhibit additional features of Duane or Mobius syndrome. Pupil, slit–lamp, dilated fundus and the remainder of the neurologic evaluations were also unremarkable. FIESTA provided a non–invasive myelographic effect with very bright CSF and the nerves and vessels of the basal cisterns appeared as "filling defects" facilitating the assessment of the abducens nerve. The right but not left abducens nerve was identified. No compressive lesion of other brain abnormality was identified, consistent with abducens nerve aplasia.
Conclusions: :
Accurate detection of the presence, course, and contour of the smaller cranial nerves has previously been challenging with MR. The FIESTA technique may allow more widespread and accurate diagnosis of disorders of the abducens and other cranial nerves and may eventually prove to be a helpful asset in elucidating their etiology and guiding their management.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • neuro-ophthalmology: diagnosis • eye movements