Cerebral aqueductal web causing hydrocephalus in a case of Neurofibromatosis type-1

Clinical History

A 5-year-old girl came with complaints of increase in size of the head with headache.
On clinical examination, the patient had multiple brown coloured café-au-lait spots on her face, forehead, hands and back.

Imaging Findings

Magnetic resonance imaging (MRI) of the brain showed patchy T2W and FLAIR hyperintensities in the cerebellar white matter and globus pallidi bilaterally s/o hamartomas.
Supratentorial gross hydrocephalus was seen, however, there was no CSF seepage in periventricular area s/o compensated hydrocephalus. The fourth ventricle was normal.
FIESTA sequence showed a linear web in the cerebral aqueduct. No enhancement was seen on post-contrast study.

Discussion

Neurofibromatosis (NF) is a neurocutaneous disease, also called Von Recklinghausen disease, which affects skin, central nervous system, eyes, bones and other sites.
There are three types of neurofibromatosis:
Type 1 (NF1) shows cutaneous brown coloured café-au-lait spots and neurofibromas. It also causes deformity of bones. It is seen in childhood.
Type 2 (NF2) shows hearing loss due to acoustic schwannomas. It is seen in teen years.
Type 3 Schwannomatosis is the rare type which causes severe pain [1].
NF is an autosomal dominant disease. The NF1 gene is located on the long arm of chromosome 17 at 17q11.2 and produces a protein called neurofibromin. This protein is responsible for lesions as it is present in schwann cells, neurons, astrocytes and oligodendrocytes [2].
Neurofibromatosis type 1 is more frequent and has an estimated incidence of one case per 2500-3500 [3].
Clinical presentation of NF1 is skin lesions, increase in size of the head, learning disabilities, bone deformities with short stature and visual disturbances.
Imaging is important to diagnose complications of NF1 as it shows a multisystem affection. It is important to diagnose neurological complications like gliomas, hamartomas which can cause hydrocephalus and vision disturbances.
MRI is useful in diagnosing intracranial complications, CT scan and plain radiographs are useful to detect bony abnormalities like sphenoid wing dysplasia and lambdoid suture defects.
1 to 5 % cases of NF1 show obstructive hydrocephalus.
Obstruction is seen due to cerebellar and pontine tegmentum hamartomas, periaqueductal and tectal hamartomas, brain stem glioma, aqueductal web, superior velum medullary synechia [4].
Aqueductal web is one of the rare causes of hydrocephalus in NF1 [5].
In this case, hamartomas were seen in cerebellar white matter and globus pallidi with no enhancement on postcontrast study. Hamartomas were not showing any mass effect over the fourth ventricle. FIESTA sagittal sections were obtained, which showed a thin cerebral aqueductal web. It is important to take high resolution thin sections of aqueduct in cases of obstructive hydrocephalus.
Treatment in NF1 is conservative as well as surgical, depending on the complications.
Hamartomas do not need to be treated surgically. Obstructive hydrocephalus can be treated by endoscopic third ventriculostomy.
Symptomatic pain medications and epilepsy medications are given in some cases. Prognosis of patients with neurofibromatosis depends on the type.
NF may reduce life expectancy by up to 15 years [6], hence prompt diagnosis by imaging and early treatment can increase life expectancy.

Differential Diagnosis List

Final Diagnosis

Aqueductal web causing obstructive hydrocephalus in NF1.

URL:	https://www.eurorad.org/case/14644
DOI:	10.1594/EURORAD/CASE.14644
ISSN:	1563-4086