Arachnoid cysts are cerebrospinal fluid-filled collections that
occur between two arachnoid layers. Although arachnoid cysts account for 1% of all intracranial space occupying lesions, the
association between arachnoid cysts and subdural hygroma is
rare and only 23 cases have been previously reported in the
literature
3,10,16-18,20-25.
The association between arachnoid cysts and subdural
hematomas was first noted in 197126,27. Although no
explanation for this predisposition has been proven, theories
have been suggested5,8. As arachnoid cysts are less
compliant than normal brain tissue the amount of intracranial
‘cushioning’ during trauma is reduced with an increased
likelihood of bridging veins to bleed. Alternatively, due to
different composition of arachnoid cyst fluid compared to
normal CSF, pressure may be transferred more readily and in
magnified form which may lead to rupture of the bridging
veins or of the vessels within the cyst wall26. In our case, the
arachnoid cyst on the anterior of left temporal region ruptured
and caused subdural hygroma with the trauma.
Arachnoid cysts may rupture spontaneously or after head
trauma. The rupture of an arachnoid cyst may produce the
rapid onset of life-threatening symptoms. Therefore; a risk of
spontaneous or traumatic rupture of arachnoid cyst should be
kept in mind in all cases with arachnoid cysts, especially if
there is suspicion of growth in size. If the cyst shows any
growth, surgical intervention should be undertaken17.
Surgery is generally recommended for symptomatic cysts
causing seizures, hydrocephalus, raised intracranial pressure or
focal deficits. Rapidly enlarging subdural hygroma and
hematoma require surgical drainage10,15,28.
Currently, there are two procedures used in the surgery;
the first is cyst fenestration and the second is a cysto-peritoneal
shunt. In patients without hemorrhage, either cysto-peritoneal
shunting or cyst fenestration could be the choice. Yet in cases
of intracystic or subdural hemorrhage, craniotomy with
hematoma evacuation and cyst fenestration is superior to cystoperitoneal
shunting10. In our cases, there was no hemorrhage;
we performed the arachnoid cyst fenestration and cystoperitoneal shunt together for the recovery of the clinical
symptoms.