Zdravniški Vestnik (Dec 2002)
ECHOGRAPHIC PICTURE OF OPTIC NERVE GLIOMA IN NEUROFIBROMATOSIS TYPE-1
Abstract
Background. Authors want to present echographic picture of orbital part of low-grade pilocytic astrocytoma involving the optic nerve and/or chiasm and optic tract (optic pathway glioma or visual pathway glioma).Methods. 4 children with neurofibromatosis type-1 complicated with optic pathway glioma diagnosed earlier with magnetic resonance were examined by ultrasound. Standardised A-scan technique was used for optic nerve width measurement. The 30° test and B-scan (axial, transverse and longitudinal sections) of both eyes and orbits were performed as well.Results. The optic nerve diameter in our cases ranged from 4.48 to 8.5 mm. Two children had the left side optic pathway glioma, one boy had the right side optic pathway glioma and in one tumour was bilateral. The transversal section of the nerve revealed dark oval and in more perpendicular sections round void of the nerve. As the beam is swept towards the orbital apex void becomes more fusiform. The nerve and its sheaths are markedly widened. An abnormal increase in reflectivity and irregularity of the spike’s pattern is exhibited as well. No calcification along the sheaths is noticed. The transverse section of the tumour demonstrated an »inverse doughnut« sign. The outer whiter outline of the widened sheaths surrounds an inner darker circle. The longitudinal section revealed the optic nerve head continuing into the widened optic nerve. The 30° test was negative. The differential diagnosis of meningeoma, optic neuritis and orbital cysticercosis should be considered.Conclusions. Ultrasound as a cheap, safe, easily repeatable imaging method should become a method of choice for screening optic nerve tumours in neurofibromatosis type-1, especially in children, as well as for follow-up after treatment.
