If the flow of fluid is obstructed at any point, it accumulates in the ventricles causing them to enlarge and compress surrounding brain tissue. Treatment may be by insertion of a 'shunt' to redirect the excess CSF or, in some cases, by a third ventriculostomy. This will entail a hole being bored in the floor of the 3rd ventricle to aid the impaired CSF flow. Symptoms caused by raised pressure usually improve, but other signs of brain damage may remain. These can include subtle learning difficulties.
Shunts can become blocked leading to headache, nausea, photophobia, inertia and irritability.
Chronic infection may cause gradual deterioration in overall performance. Medical advice should be sought if a shunt blockage is suspected. X-linked Hydrocephalus is the exception. Only boys are affected. Incidence is rare and is usually accompanied by abduction of the thumbs.