Keywords hydrocephalus - late-onset aqueductal membranous occlusion - time-SLIP
Introduction
Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant genetic
disorders in humans.[1 ] Hydrocephalus has been reported in 2 to 23% of NF1 patients, and NF1 patients rarely
present with hydrocephalus caused by late-onset aqueductal membranous occlusion (LAMO).[2 ]
[3 ]
Here, we report a similar case to LAMO. Although the membranous structure directly
covered the aqueduct in the LAMO, a thin expanded cyst wall covered the entrance of
the aqueduct in our case. The cause of the hydrocephalus was diagnosed on the basis
of the neuroendoscopic rather than the preoperative examination findings. We reviewed
the literatures about LAMO and compared our case with previously reported LAMO cases.
Case Report
A 28-year-old woman visited a nearby hospital with complaints of headache and dizziness.
Computed tomography revealed enlarged lateral ventricles. She was referred to our
hospital for further examinations. Café au lait spots and neurofibroma were observed
on her face and back. Blood and cerebrospinal fluid (CSF) examinations yielded normal
results. The patient's past medical history included systemic lupus erythematosus
and NF1. She received prednisolone, tacrolimus, and mizoribine. Magnetic resonance
imaging (MRI) revealed hydrocephalus, but no obvious intracranial lesions. MRI with
the time-spatial labeling inversion pulse (SLIP) showed no CSF flow in the aqueduct,
and obstructive hydrocephalus due to aqueductal lesion was suspected ([Figs. 1A ], [2 ]). When endoscopic third ventriculostomy (ETV) was performed, a thin membrane covering
the entrance of the aqueduct was detected ([Fig. 1B ]). In addition to ETV, we perforated the thin membrane to maintain the normal CSF
flow ([Fig. 1C ]). The membranous structure was part of the cyst wall, and the cyst was deflated
by breaking a part of the membranous structure, thereby restoring the CSF flow to
the aqueduct. Histopathologically, the cyst wall consisted of gliosis ([Fig. 1D, E ]). After the operation, the symptoms and enlargement of the ventricles were improved
([Fig. 1F ]). CSF flow was observed not through the floor of the third ventricle but through
the aqueduct on MRI with the time-SLIP ([Fig. 3 ]). No recurrence of hydrocephalus was observed for 4 years after the surgery.
Fig. 1 (A ) Preoperative T2-weighted magnetic resonance image showing the enlarged ventricles
and no intracranial lesions. (B ) Intraoperative view showing the thin cyst (red arrowhead , the edge of the cyst wall) covering the entrance of the aqueduct (yellow arrow ). (C ) The membrane covering the aqueduct is perforated, and the cerebrospinal fluid flow
is improved. The red and yellow arrowheads indicate the edge of shrank cyst wall;
the entrance of the aqueduct, respectively. (D ) The pathological findings from the hematoxylin and eosin staining (original magnification × 40)
showing astrocytes with irregular nuclei. Neither mitosis nor necrosis was detected.
(E ) Staining positive for glial fibrillary acidic protein (original magnification × 40).
(F ) Postoperative T2-weighted magnetic resonance image showing the improvement of the
ventricles size.
Fig. 2 Preoperative magnetic resonance image with time-spatial labeling inversion pulse
showing no cerebrospinal fluid flow from the third ventricle to the aqueduct (red arrow ).
Fig. 3 Postoperative magnetic resonance image with time-spatial labeling inversion pulse
showing cerebrospinal fluid flow signal not through the floor of the third ventricle
(yellow arrow ) but through the aqueduct (red arrow ).
Discussion
Matsuda et al first described LAMO in 2011.[2 ] Terada et al defined LAMO as follows[3 ]: first, the aqueduct of Sylvius showed a membranous structure but no CSF flow; second,
no other occlusive lesion and no recent subarachnoid hemorrhage, intraventricular
hemorrhage, or meningitis was found that could cause the hydrocephalus; third, the
lateral and third ventricles were enlarged, but the fourth ventricle was not; and
fourth, the patient was not diagnosed in childhood. No membranous structure was found
in the aqueduct of Sylvius in our case, but it was a similar case to LAMO. In our
case, the membranous structure covered the entrance of the aqueduct by expanding like
a cyst. Gliosis, forking, simple stenosis, or membranous occlusion was considered
to be the cause of the aqueductal stenosis or occlusion in the past report.[4 ]
[5 ] Our histopathological findings from the cyst wall were also consistent with gliosis.
The surgical treatment of LAMO is mainly endoscopic aqueductoplasty (EA) and/or ETV,
which have an advantage of improving hydrocephalus without shunt system insertion.[2 ]
[3 ]
[6 ]
[7 ] We performed EA and ETV because the patient took immunosuppressive drugs, and we
were concerned of a possible shunt infection.
We summarize 12 cases consistent with LAMO in [Table 1 ].[2 ]
[3 ]
[6 ]
[7 ] The main symptom was headache, and the oldest patient was 66 years old. Only EA
was performed in eight cases, and EA + ETV was performed in four cases. The chief
complaints were improved in eight cases (66.6%). Of the EA + ETV cases, two (50%)
had complications, but only the EA cases had no complications. The postoperative CSF
flow was studied in Terada's case and in our case using MRI with a three-dimensionally
driven equilibrium pulse and time-SLIP, respectively.[3 ] CSF flow was detected in the third ventricular floor and aqueduct in a former case
and only in the aqueduct in our case. According to the postoperative CSF flow analysis
of two cases, performing aqueductoplasty to restore the physiological CSF flow would
be more important than performing ETV alone in cases like LAMO. Our case did not show
a reocclusion for 54 months despite that no postoperative CSF flow was observed in
the third ventricle floor.
Table 1
Review of clinical results of late-onset aqueductal membranous occlusion treated by
endoscopic ventriculostomy and/or aqueductoplasty
Author (y)
Age/sex
Symptoms
Operation (complication)
Outcome (follow-up [mo])
Postoperative ventricular size
Postoperative CSF flow
Schroeder and Gaab (1999)6
31/F
Headache, nausea, vomiting, blurred vision, seizure
EA
Occasional headache (18)
Smaller
N/A
46/F
Headache, mental deterioration
EA
Unchanged (7)
Smaller
N/A
66/M
Mental deterioration, gait disturbances, urinary incontinence, alcohol abuse
EA
Unchanged (1)
Unchanged
N/A
66/F
Headache, mental deterioration, gait disturbances, urinary incontinence,
EA + ETV
(Fornix contusion)
Died after stroke (1)
Unchanged
N/A
Matsuda et al (2011)2
57/M
Gait disturbances, dementia
EA + ETV
Improved (7)
Unchanged
N/A
Chen et al (2013)7
20/M
Headache, vomiting
EA
Improved (16 ≤)
N/A
N/A
24/F
Headache, vomiting
EA
Improved (16 ≤)
N/A
N/A
26/M
Headache, vomiting
EA
Improved (16 ≤)
N/A
N/A
28/F
Headache, vomiting
EA
Improved (16 ≤)
N/A
N/A
33/F
Headache, vomiting
EA
Improved (16 ≤)
N/A
N/A
Terada et al (2020)3
36/M
Headache, loss of consciousness
EA + ETV (diplopia)
Improved (N/A)
Smaller
CSF flow in the third ventricular floor and aqueduct
Our case
28/F
Headache, dizziness
EA + ETV
Improved (54)
Smaller
CSF flow in the aqueduct
Abbreviations: CSF, cerebrospinal fluid; EA, endoscopic aqueductoplasty; ETV, endoscopic
ventriculostomy; F, female; M, male; N/A, not available.
The histopathological findings from the cyst wall in our case were consistent with
gliosis and suggested a relationship between the cyst formation and the membranous
structure of the aqueduct in the previous report.[4 ]
[5 ]
In the other reports, the membranous structure in the aqueduct was detected on the
preoperative MRI, but our case did not show obvious causes in the radiological images.[2 ]
[3 ]
[6 ]
[7 ] It was considered that the cyst wall of the gliosis was so thin that it could not
be identified on the preoperative MRI. If LAMO was suspected, endoscopic treatment
might be available to find and treat unknown causes in the imaging examinations and
obtain a good clinical result for a long time without shunt insertion.
Conclusion
When suspecting cases similar to LAMO, neuroendoscopic surgery might have an advantage
in the diagnosis of unknown causes by preoperative MRI, and the hydrocephalus could
be treated without shunt insertion for a long time.
