Raised intracranial pressure

Question 1

What is the aetiology of raised intracranial pressure? (x7)

Answer 1

• Vascular: haemorrhage (extradural, subdural, SA, intracerebral), obstruction to venous drainage such as venous sinus thromboses
• Infection: meningitis, encephalitis (causes damage to arachnoid granulations, impairing CSF flow), abscess
• Trauma
• Tumours
• Hydrocephalus
• Endocrine disorders: Addison’s disease, hypoparathyroidism, corticosteroid withdrawal
• Idiopathic aka. pseudotumor cerebri

Question 2

What are the signs and symptoms of raised intracranial pressure? (x8)

Answer 2

• Headaches: pulsatile, may have nausea association, rarely vomiting
• Pulse-synchronous tinnitus: highly specific, often unilateral
• Transient visual obscuration (episodes of visual loss for 30 seconds – may be unilateral or bilateral). The cause is transient ischaemia of the optic nerve head
• Visual loss – inferonasal (can be acute or chronic)
• Papilledema
• False localising signs
• Photophobia
• Neck and back pain

Question 3

What are the investigations for raised intracranial pressure? (x5)

Answer 3

• Visual field testing: enlarged blind spot, inferonasal loss, constriction of field
• Ophthalmoscopy: papilledema
• MRI: empty sella and flattening of the globe
• LP: raised opening CSF pressure

Question 4

What is visual field testing called?

Answer 4

Perimetry

Question 5

What are false localising signs? Classic example?

Answer 5

In majority of patients, a particular neurological sign indicating pathology at a specific locus or pathway within the nervous system. False localizing signs refer to neurological signs that reflect pathology distant from the expected anatomical locus which make challenges in traditional clinicoanatomical correlation. For example, sixth cranial nerve palsy

Question 6

What are CNS tumours?

Answer 6

Primary tumours arising from CNS

Question 7

What is the aetiology of CNS tumours?

Answer 7

Children: embryonic errors in development; Adults: unknown

Question 8

What are the types of CNS tumour? (x9)

Answer 8

• Meningioma: benign, arising from meningothelial cells of arachnoid layer
• Glioma: tumours that arise from glial cells (provide support and protection in CNS). Examples include astrocytic tumours, oligodendrogliomas (produce myelin in CNS; these are epileptogenic) and ependymomas (ependymal cells line spinal cord and ventricles and help produce and circulate CSF with their cilia)
• Astrocytic tumours: arising from astrocytes, examples include fibrillary astrocytoma usually in cerebrum, and pilocytic astrocytoma, a cystic tumour usually in cerebrum and brainstem
• Acoustic neuroma: benign, cerebellopontine angle tumour, arising from vestibulocochlear nerve
• Medulloblastoma: malignant, invasive, midline cerebellar tumour in children
• Glioblastoma multiforme: high-grade, invasive, unknown cellular origin
• Hemangioblastoma: benign vascular tumours, usually in cerebellum
• Pituitary adenoma: benign, space-occupying, endocrine effects
• Lymphoma: non-Hodgkin’s

Question 9

What is the epidemiology of CNS tumours: Age? Most common type?

Answer 9

Bimodal distribution of children and elderly. Most common is meningioma.

Question 10

GENERAL: What are the signs and symptoms of CNS tumours? (x3)

Answer 10

• Raised ICP: headache, papilledema, nausea, false localising signs
• Epilepsy
• Focal neurological deficits such as dysphagia, hemiparesis, ataxia, visual field defects, cognitive impairment, hemianopia

Question 11

! What are the localising signs and symptoms of CNS tumours: Olfactory groove? Cavernous sinus? Pituitary fossa? Para-sagittal region? Cerebellopontine angle?

Answer 11

• OLFACTORY GROOVE: anosmia, frontal lobe dysfunction
• CAVERNOUS SINUS: ophthalmoplegia (III, IV, VI nerve palsies), V1 and V2 sensory loss
• PITUITARY FOSSA: bitemporal hemianopia (suprasellar expansion and optic chiasm compression), hypopituitarism or hypersecretion of specific hormones (acromegaly, hyperprolactinaemia, Cushing’s disease)
• PARA-SAGITTAL REGION: spastic paraparesis (mimicking cord compression)
• CEREBELLOPONTINE ANGLE: unilateral deafness, facial weakness, then unilateral ataxia and hemifacial sensory impairment

Question 12

What is Foster Kennedy syndrome?

Answer 12

Sphenoid wing meningioma compresses CNII causing ipsilateral optic atrophy and contralateral papilledema.

Question 13

What is Parinaud’s syndrome?

Answer 13

Pineal region tumour, sunset sign, upward gaze palsy (if superior midbrain lesion), or obstructive hydrocephalus (if at level of third ventricle)

Question 14

What are the investigations for CNS tumours?

Answer 14

• CT: initial investigation if concerned about acute setting or differentials including haemorrhage
• MRI: diagnostic method. Surrounding oedema
• CXR/CT (thorax, abdomen, pelvis): to determine if lesion primary or secondary
• BLOOD: CRP, ESR, consider HIV screen, toxoplasma serology
• BRAIN BIOPSY: type and grading

Question 15

Lumbar puncture in CNS tumour?

Answer 15

Relative contraindication if there is evidence of raised CIP, since tumours may cause this. In these cases, LP would cause CONING (herniation)

Question 16

What can be added to an MRI in CNS tumour investigations? (x3)

Answer 16

Diffusion-weighted-imaging (maps diffusion of water in brain – tumours receive higher amounts of water), MR spectroscopy (studies metabolic changes) can be helpful in characterising lesion without biopsy. Functional MRI may be needed if in dominant hemisphere for surgical planning

Question 17

What is hydrocephalus?

Answer 17

Enlargement of cerebral ventricular system

Question 18

What are the types of hydrocephalus? (x2)

Answer 18

OBSTRUCTIVE: abnormal accumulation of CSF caused by OBSTRUCTION of CSF flow; NON-OBSTRRUCTIVE (COMMUNICATING): impaired CSF resorption in the subarachnoid granulations (found along superior sagittal sinus) back into the venous system

Question 19

What is hydrocephalus ex vacuo?

Answer 19

Apparent enlargement of ventricles but a compensatory change due to brain atrophy.

Question 20

What is the aetiology of obstructive hydrocephalus? (x2 and (x5))

Answer 20

• Abnormal accumulation of CSF caused by OBSTRUCTION of CSF flow
• Congenital causes: cerebral aqueduct stenosis, neural tube defects
• Acquired causes: lesions of the third ventricle, fourth ventricle or cerebral aqueduct from infection, trauma, tumour, toxoplasmosis or haemorrhage, or fourth ventricle compression from posterior fossa lesions.

Question 21

What is the aetiology of communicating hydrocephalus? (x4)

Answer 21

• Impaired CSF resorption due to functional impairment of subarachnoid granulations (aka villi)
• Subarachnoid haemorrhage
• Meningitis (typically TB)
• Leptomeningeal carcinomatosis where brain cancer spreads to meninges
• Normal pressure hydrocephalus (NPH): idiopathic chronic ventricular enlargement where the long white matter tracts are damaged causing gait and cognitive decline symptoms, but without the raised CSF pressure expected in hydrocephalus

Question 22

What is the epidemiology of hydrocephalus: Age?

Answer 22

Bimodal from congenital malformations and tumours in the young, and STROKES in the elderly

Question 23

What are the signs and symptoms of hydrocephalus?

Answer 23

• All relate to raised ICP:
• Acute drop in consciousness
• Diplopia, papilledema, false localising signs such as CNVI palsy
• Enlarged head circumference in neonates and bulging fontanelles
• Sunset sign (downward conjugate deviation of eyes – eyes appear driven downward so that inferior iris is covered by eyelid creating a sunset)

Question 24

What are the signs and symptoms of NPH? (x4)

Answer 24

Hakim’s triad of gait instability, urinary incontinence, and dementia (chronic cognitive decline). Hyperreflexia

Question 25

What are the investigations for hydrocephalus? (x2)

Answer 25

• CT HEAD: first line, showing ventricular enlargement
• CSF: obtained from ventricular drains of LB; may indicate underlying pathology such as TB. However, LP contraindicated in patients other than NPH due to raised ICP and risk of herniation

Question 26

What additional investigation is there for NPH?

Answer 26

Levodopa administration. Levodopa-unresponsive gait apraxia excludes Parkinson’s.