hydrocephalus is the most common type of hydrocephalus in the neonatal
period. Posthemorrhagic hydrocephalus may be communicating or noncommunicating.
It is usually the consequence of intraventricular hemorrhage. Intraventricular
hemorrhage usually occurs as a consequence of germinal matrix hemorrhage.
Germinal matrix hemorrhages are unusual after 34 weeks gestational age.
Germinal matrix hemorrhages are classified based on brain ultrasound in
four grades. Grade I intraventricular hemorrhage refers to the presence
of subependymal bleed; Grade II intraventricular hemorrhage refers to
extension of the subependymal bleed into the ventricles but without ventricular
dilatation; Grade III intraventricular hemorrhage refers to subependymal
bleed with extension of the bleed into the ventricles and hydrocephalus;
and Grade IV intraventricular hemorrhage refers to subependymal bleed
with extension of the bleed into the parenchyma as a result of venous
Hydrocephalus following intraventricular
hemorrhage can occur within days of a bleed (acute), more than a week
later (subacute), or as late as 3 months after the bleeding (chronic).
Acute hydrocephalus may be communicating
or noncommunicating. Acute communicating hydrocephalus occurs with large
intraventricular hemorrhages due to obstruction of the arachnoid villi
by blood clots. Acute noncommunicating hydrocephalus is due to obstruction
by blood clots of the ventricular system at any of its narrow passages.
hydrocephalus (the term posthemorrhagic hydrocephalus is often reserved
for this type of hydrocephalus) is usually communicating. It occurs with
small and large hemorrhages. It is due to obstruction of the subarachnoid
space. The obstruction occurs at the tentorial notch. The arachnoid adhesions
block the normal flow of cerebrospinal fluid to the convexity of the brain.
Chronic hydrocephalus may be
communicating or noncommunicating. It occurs with small and large hemorrhages.
Communicating hydrocephalus results from permanent scarring of the corpuscle
of Pachioni. Noncommunicating hydrocephalus results from disrupted ependyma
or reactive gliosis. The blood clot or reactive gliosis obstructs the
ventricular system at any of its narrow passages.
The diagnosis of hydrocephalus
in the premature newborn is made by ultrasound. Computed tomography and
MRI of the brain offer additional information that may help to define
the site of obstruction. There is no general consensus regarding the best
way to manage these patients. Serial lumbar punctures do not prevent hydrocephalus.
They are used because they delay the need for ventricular drainage, thus
allowing time for spontaneous resolution of the blockage. Fibrinolytic
therapy is promising but its use is not recommended. Neonates with posthemorrhagic
hydrocephalus may present with: (1) excessive increase in head circumference
(>1 cm/week); (2) excessive increase in head circumference associated
with a tense fontanelle; (3) ultrasonographic evidence of increased ventricular
size without any other signs; (4) neurological signs of increased intracranial
pressure such as encephalopathy or increased musculoskeletal reflexes;
or (5) cardiovascular signs of increased intracranial pressure such as
tachycardia and hypotension. The latter two presentations are infrequent.