Neurology: Hydrocephalus, SOL Flashcards
What causes hydrocephalus (water in the brain)?
Abnormal increase in the volume of CSF and size of the cerebral ventricles (ventriculomegaly)
What are the two types of hydrocephalus?
1) Obstructive hydrocephalus
2) Communicating hydrocephalus
How causes obstructive hydrocephalus?
1) CSF cannot exit the ventricular system
2) This causes dilation of the ventricles up-stream
Where are the places obstruction can occur in obstructive hydrocephalus and what is an example of a cause at each of these places?
1) Foramen of Monro e.g. colloid cysts
2) Cerebral aqueduct e.g. aqueduct stenosis - common cause
3) Fourth ventricle e.g. posterior fossa tumour
What causes communicating hydrocephalus?
CSF can exit the ventricular system but there is an obstruction to CSF absorption at the subarachnoid space
What are two common causes of communicating hydrocephalus?
1) Subarachnoid haemorrhage
2) Infective meningitis
How does hydrocephalus typically present?
Features of raised ICP e.g. early morning headache, N&V (+ ventriculomegaly on CT if obstructive)
How can you treat hydrocephalus?
Use shunts to drain the extra CSF into the heart or peritoneal cavity
What condition would show dilated lateral ventricles and third ventricle but relatively normal fourth ventricles (obstructive hydrocephalus) on CT scan?
Cerebral aqueduct stenosis (obstruction between third and fourth ventricles) - the aqueduct connects the third and fourth ventricles so the fourth ventricles will be of a relatively normal size
Which two ventricles does the cerebral aqueduct connect?
Third and fourth ventricles
What commonly causes cerebral aqueduct stenosis?
Congenital - presents in younger patients e.g. 30
Which type of hydrocephalus is associated with ventriculomegaly?
Obstructive
What investigation do you do for hydrocephalus?
CT scan
What treatment can be used to decrease ICP as a result of cerebral oedema?
Mannitol - increases cerebral blood flow
How can a cranial space occupying lesion present?
1) Prominent worsening headache - worse on waking, lying down, coughing/straining, associated with vomiting
2) Non-specific early signs of raised ICP - headache + morning N&V
3) Cranial nerve palsies - unsteadiness, double vision, abducens palsy
4) Cushing’s reflex
5) Progressive focal neurological signs e.g. subacute onset left leg weakness, increased tone, brisk reflexes
5) Advanced cases - drowsiness, seizure activity, pupillary abnormalities, bilateral papilloedema, hypertension
6) Night sweats
Which cranial nerve is particularly affected by space occupying lesions and why?
Abducens nerve (CN VI)
1) Exits the ventral pons and travels upwards before protruding forward through the cavernous sinus
2) Therefore it is compressed against the sphenoid bone as pressure from above increases
What are symptoms of the Cushing’s reflex?
1) Raised BP
2) Bradycardia
3) Abnormal breathing incl. Cheyne-Stokes respiration (cyclical episodes of apnea and hyperventilation)
What are the four differential diagnoses/major groups of causes of space occupying lesions?
1) Tumours (space occupying neoplasia) - metastatic disease and primary CNS tumours
2) Vascular lesions
3) Infective processes
4) Granulomata
Which primary cancers typically metastasise to the brain causing SOL?
Breast, lung, melanoma
What are the two types of primary CNS tumours?
1) Benign e.g. meningiomas
2) Malignant e.g. glioblastoma multiforme
Why can all CNS tumours be life threatening (even if they are benign)?
Bc of the tight physical constraints of the cranial vault
What are examples of infective processes leading to SOL?
1) Cerebral abscesses
2) Rarer diseases e.g. cysticercosis, amoebiasis, TB
Which patients are more prone to intra-cerebral infections?
Patients who are immunosuppressed - so look for risk factors e.g. HIV
Which investigation might be indicated in ambiguous SOL cases?
Biopsy of the lesion
