Hydranencephaly: A Rare Cause of an Enlarging Head Size in an Infant

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North American Journal of Medical Sciences | October 2012 | Volume 4 | Issue 10 |
520
Letter to Editor
Hydranencephaly:
A Rare Cause of an
Enlarging Head Size in
an Infant
Dear Editor,
Hydranencephaly is a rare congenital abnormality
characterized by absence and replacement of the cerebral
hemispheres by a large cerebrospinal uid pool. It is
thought to be caused by occlusion of bilateral internal
carotid arteries in the fetal life mainly during the second
trimester due to a variety of causes.[1,2] It is one of the
recognized forms of brain malformations which is
usually associated with intrauterine fetal demise and is
therefore rarely seen in postnatal life.[3] It is a rare entity
with a reported incidence of less than 1 per 10,000 live
births.[4]
A 4‑month‑old preterm infant was brought by his parents
to the pediatric outpatient department with complaints
of recent onset of fever and progressively enlarging
head size. The fever was of moderate degree and was
not associated with chills and rigors. According to the
parents, the size of the baby’s head was normal at the
time of birth but it started increasing after one week of life.
On examination, the child was lethargic with increased
occipito‑frontal circumference and there was hypotonia
in all the four limbs. There was no associated cranio‑facial
dysmorphism or limb deformity. The mother also reported
that the eyes of the child showed roving movement.
The primitive reexes, such as grasp and suction, were
intact. He responded only to sound and painful stimuli
and a lack of awareness to the surroundings was noted.
The fundus examination of the child was normal. The
mother was neither diabetic nor hypertensive; she was
not a smoker and had never ingested alcohol. There was
no history of radiation exposure or febrile illness and
exanthematous skin rash during pregnancy. She did not
undergo any ultrasound examination during the antenatal
period. There was no history of consanguinity or similar
complaints in the other siblings. After admission, he
was managed with a working diagnosis of complicated
tubercular meningitis. Mantoux test and CSF examination
were normal. The baby was then referred for computed
tomography (CT) of the head.
Axial CT of the head showed complete absence of B/L
cerebral hemispheres with no cortical mantle and their
replacement by uid [Figure 1]. However, entire falx
was preserved excluding holoprosencephaly. Also
thalamus, pons, medulla, and cerebellar hemispheres
were relatively preserved [Figure 2], all in keeping
with the diagnosis of hydranencephaly. Somatosensory
evoked potentials (SSEP) showed complete absence
of the cortical activity with preservation of waves of
brainstem origin. Electroencephalogram revealed a
at pattern. The visual evoked potential was absent
bilaterally. The parents of the baby were counseled for
poor prognosis of the condition and the minimal risk of
recurrence in subsequent pregnancies. They refused any
active surgical intervention.
Hydranencephaly is a rare encephalopathy that occurs
in‑utero and presents rarely in postnatal period.
The posterior fossa structures as well as parts of the
temporal and occipital lobe supplied by posterior
cerebral arteries are usually preserved.
[1,5] However,
cases with cerebellar hypoplasia and occlusion
of bilateral posterior cerebral arteries have been
reported.[1] This rare disorder usually occurs after
ventricles have already formed; hence, the falx is
preserved. Hydranencephaly is associated with various
congenital anomalies, including arthrogryposis,
renal aplastic dysplasia, poly‑valvular heart defect,
trisomy 13 and Fowler syndrome.[6]
Most common etiologies described for hydranencephaly
are occlusion of the supra‑clinoid segment of bilateral
internal carotid arteries,[1] or an extreme form of
leukomalacia formed by confluence of multiple
cystic cavities. Other etiologies include fetal hypoxia
due to maternal exposure to carbon monoxide or
butane gas resulting in massive tissue necrosis with
cavitation and resorption of necrotized tissue and
necrotizing vasculitis or local destruction of the
brain tissue secondary to intrauterine infections, e.g.
congenital toxoplasmosis, cytomegalovirus and herpes
simplex.[4,7]
Hydranencephaly can be diagnosed using ultrasound
(ante‑ and postnatal), Magnetic Resonance
Imaging (ante‑ and postnatal) and CT. The radiological
features include almost complete absence of cortical
mantle. The cranium is completely filled with
membranous sac containing cerebrospinal uid. The
skull may be normal‑sized or enlarged as was seen
in the present case. The falx cerebri and tentorium
cerebelli are usually intact. Thalamus, hypothalamus
and choroid plexus are preserved and cerebellum is
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Letter to Editor
North American Journal of Medical Sciences | October 2012 | Volume 4 | Issue 10 | 521
intact.[1,4] The electrophysiological studies conrm the
imaging ndings. Prolonged survival upto 22 years has
been reported in literature with signicant associated
morbidity.[3,8] Ventriculo‑peritoneal shunting has been
tried with limited success because of frequent need for
shunt revision or removal and associated poor prognosis
for psychomotor development.[9] Recently, endoscopic
choroid plexus coagulation is being explored as an
alternative to shunting.[10]
The condition needs to be differentiated from severe
obstructive hydrocephalus and severe open lip
schizencephaly, however, in both these conditions,
the cortical mantle is only reduced in thickness.
Alobar holoprosencephaly can be differentiated by the
presence of falx and frequent coexisting midline facial
abnormalities.
Thus, hydranencephaly should also be considered
in the differential diagnosis of an infant presenting
with enlarging head size, especially in children with
psychomotor retardation.
Mohd Khalid, Saifullah Khalid,
Samreen Zaheer, Navneet Redhu,
Ekramullah
Department of Radiodiagnosis,
Jawaharlal Nehru Medical College and Hospital, AMU,
Aligarh, India. E‑mail: saif2k2@gmail.com
References
1. Kelly TG, Sharif UM, Southern JF, Gururajan K, Segall HD. An
unusual case of hydranencephaly presenting with an anterior
midline cyst, a posterior calcied mass, cerebellar hypoplasia
and occlusion of the posterior cerebral arteries. Pediatr Radiol
2011;41:274‑7.
2. Stevenson DA, Hart BL, Clericuzio CL. Hydranencephaly
in an infant with vascular malformations. Am J Med Genet
2001;104:295‑8.
3. McAbee GN, Chan A, Erde EL. Prolonged survival with
hydranencephaly: Report of two patients and literature
review. Pediatr Neurol 2000;23:80‑4.
4. Kurtz AB, Johnson PT. Diagnosis please. Case 7:
Hydranencephaly. Radiology 1999;210:419‑22.
5. Taori KB, Sargar KM, Disawal A, Chhadi S, Rathod J.
Hydranencephaly associated with cerebellar involvement
and bilateral microphthalmia and colobomas. Pediatr Radiol
2011;41:270‑3.
6. Usta IM, AbuMusa AA, Khoury NG, Nassar AH. Early
ultrasonographic changes in Fowler syndrome features and
review of the literature. Prenat Diagn 2005;25:1019‑23.
7. Christie JD, Rakusan TA, Martinez MA, Lucia HL,
Rajaraman S, Edwards SB, et al. Hydranencephaly caused by
congenital infection with herpes simplex virus. Pediatr Infect
Dis 1986;5:473‑8.
8. Bae JS, Jang MU, Park SS. Prolonged survival to adulthood of
Figure 1: Non-contrast axial CT image shows (a) complete destruction of bilateral cerebral hemispheres with no evidence of cortical mantle
with preserved midbrain and (b)falx cerebri
Figure 2: Non-contrast axial CT image shows relatively normal
cerebellar hemispheres, brainstem, and bilateral thalami
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Letter to Editor
North American Journal of Medical Sciences | October 2012 | Volume 4 | Issue 10 |
522
Access this article online
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DOI:
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an individual with hydranencephaly. Clin Neurol Neurosurg
2008;110:307‑9.
9. Adeloye A. Hydranencephaly in Malawian children. East Afr
Med J 2000;77:316‑8.
10. Sandberg DI, Chamiraju P, Zoeller G, Bhatia S, Ragheb J.
Endoscopic choroid plexus coagulation in infants with
hydranencephaly or hydrocephalus with a minimal
cortical mantle. Pediatr Neurosurg 2012. Jul 21. (Epub ahead
of print)
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