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|Year : 2016 | Volume
| Issue : 6 | Page : 1384-1387
Rare case of non-neoplastic aqueductal stenosis due to web in a patient with neurofibromatosis type-1
Prerna Garg, KM Shruthi, V Maheshwaran, B Devanand
Department of Radiodiagnosis, PSG Institute of Medical Sciences and Research, Peelamedu, Coimbatore, Tamil Nadu, India
|Date of Web Publication||11-Nov-2016|
Department of Radiodiagnosis, PSG Institute of Medical Sciences and Research, Peelamedu, Coimbatore - 641 004, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Garg P, Shruthi K M, Maheshwaran V, Devanand B. Rare case of non-neoplastic aqueductal stenosis due to web in a patient with neurofibromatosis type-1. Neurol India 2016;64:1384-7
|How to cite this URL:|
Garg P, Shruthi K M, Maheshwaran V, Devanand B. Rare case of non-neoplastic aqueductal stenosis due to web in a patient with neurofibromatosis type-1. Neurol India [serial online] 2016 [cited 2020 Aug 15];64:1384-7. Available from: http://www.neurologyindia.com/text.asp?2016/64/6/1384/193836
A 15-year-old girl presented with symptoms of persistent headache, blurring of vision, and watering of the left eye of 2-day duration. Two episodes of forceful vomiting were also reported. On enquiry, there was history of some surgery along the left aspect of the head to remove a tumor. On examination, multiple swellings were seen over the right arm, left thigh, and back. The deep tendon reflexes were normal. No meningeal signs could be elicited. The ophthalmological evaluation revealed bilateral iris nodules. Bilateral temporal disc pallor and mild sclerosis of peri-papillary vessels were also observed.
Magnetic resonance imaging (MRI) revealed moderate-to-severe dilatation of bilateral lateral and third ventricles with a normal appearing fourth ventricle [Figure 1]. Bilateral peri-ventricular T2-weighted hyperintense areas suggestive of trans-ependymal edema were noted [Figure 1]. The proximal aqueduct showed funnelling with a linear transverse web in the distal aqueduct on T2-weighted thin section sagittal images [Figure 2]. Normal flow void of the aqueduct was lost. Patchy non-enhancing areas of T2-weighted/fluid-attenuated inversion recovery (FLAIR) hyperintensity and T1-weighted hypo to isointensity were seen in bilateral cerebellar hemispheres, bilateral superior, and middle cerebellar peduncles, right aspect of midbrain tegmentum, right aspect of medulla, and right ganglio-capsular regions [Figure 1] and [Figure 3]. Mild mass effect on the fourth ventricle was noted distorting the fourth ventricle contour [Figure 3].
|Figure 1: (a) T2-weighted axial image shows moderate dilatation of lateral ventricles, large arrow pointing toward the right lateral ventricle; (b-d) T2-weighted axial image shows hyperintense areas around the fourth ventricle in superior cerebellar peduncles (thin arrow), cerebellum (arrow head), and medulla (dotted arrow)|
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|Figure 2: Mid-sagittal T2-weighted image shows, funneling of proximal aqueduct with a linear transverse web seen in the distal aqueduct (arrow)|
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|Figure 3: (a and b) T1-weighted post-contrast axial images show non-enhancing hypointense lesions; mild mass effect on fourth ventricle was noted distorting the fourth ventricle contour (solid arrows). Subgaleal and subcutaneous thickening is seen along the left temporo-occipital regions extending into pre and retroauricular regions, with irregularity of outer table of occipital and temporal bones (dotted arrow)|
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Subgaleal and subcutaneous thickenings were seen along the left temporo-occipital regions extending into pre and retro-auricular regions, with irregularity of the outer table of occipital and temporal bones. Suspicious focal discontinuity was noted in the left occipital bone. These findings could be attributed to a past history of surgery. Cerebrospinal fluid (CSF) flowmetry showed absent flow in the aqueduct [Figure 4].
|Figure 4: (a) Re-phased through plane image at the level of aqueduct shows no flow through the aqueduct; (b) magnitude in plane image shows no flow through the aqueduct; (c) phase in plane image shows no flow through the aqueduct|
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Based on MRI findings, a diagnosis of obstructive triventricular dilatation due to aqueductal stenosis caused by aqueductal web was established. In addition, non-enhancing T2-weighted/FLAIR hyperintensities in the brain stem, cerebellum, and left ganglio-capsular regions were in all likelihood representing hamartomas.
On further inquisition, it was established that the child's father was a known case of neurofibromatosis type-1 (NF-1). The previous surgery could be to remove a plexiform neurofibroma as past surgical details were not available. In addition, based on the presence of iris nodules and multiple swellings on the body, a diagnosis of NF-1 was made based on the established criteria.  In order to alleviate the symptoms of raised intracranial tension, a right-sided ventriculo-peritoneal shunting was performed. The patient has been on a regular follow-up.
NF is a complex heritable disorder of control of cell division which results in varied peripheral and central nervous system abnormalities. Though various forms of NF have been described, NF-1 is the most common and accounts for approximately 90% of the cases and can easily be diagnosed based on the clinical and imaging criteria.
Obstructive hydrocephalus in neurofibromatosis is a rare but known entity, with an incidence of approximately 1–5%., In the past, the main reported cause of obstructive hydrocephalus was the development of posterior fossa tumors. However, with advances in imaging techniques, the tumors are often identified before the development of hydrocephalus, and several cases of non-tumoral hydrocephalus are also identified. Aqueductal stenosis in neurofibromatosis can be due to peri-aqueductal gliosis secondary to hamartomatous proliferation, obstructing hamartomas, or gliomas.,,, It is also known that primary aqueductal stenosis in the absence of hamartomas may also occur with a higher rate of incidence in NF-1 as compared to the general population.
Obstructive hydrocephalus in NF-1 secondary to aqueductal webs have previously been reported only twice by S. Van. Es et al., and Dincer et al. The review of these cases is presented in [Table 1] along with a comparison with our case. The mechanism of development of the web is unknown as it develops insidiously and may not present in the initial years.
Three-dimensional T2-weighted images often help in identifying obstructing hamartomas as well as webs and synechiae. CSF flow studies demonstrate absence of to-and-fro flow through the aqueduct.
In conclusion, non-neoplastic aqueductal stenosis due to the presence of a web in patients with neurofibromatosis is a rare entity. It can be reliably identified on MRI, which should be the imaging of choice for diagnosis as well as follow-up. It is essential to identify this condition as an early shunt provides an excellent and long-term alleviation of symptoms.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]