raised ICP
Raised intracranial pressure is a pathological increase in the intracranial pressure and is a medical emergency.
Clinical presentation
The symptoms and signs of raised intracranial pressure are often non-specific and insidious in onset:
- headache
- drowsiness
- anorexia
- visual disturbances
- blurred vision: often the first manifestation noted by patients
- visual field loss: early finding
- visual acuity is usually preserved
- double vision
- "greying out of vision" a.k.a. transient visual obscurations
- commonly occur with changes in posture
- papilledema
- neck/back pain
- nausea and/or vomiting
- convulsions
- pulsatile tinnitus
- blackouts
- decreased GCS/coma
Pathology
Etiology
- congenital
- iatrogenic
- neurosurgery
- therapeutic agents
- idiopathic intracranial hypertension (IIH)
- infection
- meningitis
- encephalitis
- abscess
- empyema (epidural/subdural)
- trauma
- neoplasms
- primary
- metastases
- cerebrovascular
- dural sinus thrombosis
- aneurysm
- arteriovenous malformation (AVM)
- intracranial hemorrhage
Radiographic features
It follows from the Monro-Kellie doctrine that as the CSF pressure inside the skull increases, the brain and blood volume have to accommodate this, resulting in the phenomenon of mass-effect, explaining the findings of raised intracranial pressure on cross-sectional brain imaging:
- effacement of the ventricles, basal cisterns and other CSF spaces
- brain herniation
- loss of grey-white matter differentiation
Ultrasound
Point-of-care ocular sonography is commonly used in emergency settings as a swift and non-invasive screening modality for the presence of elevated intracranial pressure (ICP). Fluctuations in intracranial pressure may be assessed with serial transcranial Doppler (TCD) examinations, interrogating flow patterns in the middle cerebral artery (MCA) using pulsed wave Doppler (PWD).
Sonographic features suggestive of elevated intracranial pressure include:
- increased optic nerve sheath diameter (ONSD)
- increased specificity achieved with a "30 degree test"
- test considered positive with a 10% (or greater) reduction in OSND diameter with 30 degree lateral gaze
- increased specificity achieved with a "30 degree test"
- discrete, anechoic fluid collection within optic nerve sheath
- tracks between optic nerve and surrounding sheath
- fluid collection tends to assume roughly semilunar margins
- referred to as the crescent sign
- elevation of the optic disk
- as visualized during funduscopy (papilledema)
- elevated disk visualized at the posterior globe as a convexity protruding into the vitreous
- measured elevation should be >0.6 - 1.0 mm
- progressive elevation in cerebral vascular resistance
- the ipsilateral MCA may be visualized using a transtemporal sonographic window, and the following values recorded:
- peak systolic velocity (PSV)
- peak diastolic velocity (PDV)
- mean flow velocity (Vmean)
- results of increasing ICP manifest as the following
- decreasing mean flow velocities
- increasing pulsatility index (PI): normal MCA range 0.6 - 1.0
- an MCA PI >2.0 suggestive of ICP >20 mmHg
- the ipsilateral MCA may be visualized using a transtemporal sonographic window, and the following values recorded:
Treatment and prognosis
Specific treatment relates to the underlying etiology.
Unsurprisingly prognosis is often poor.
Complications
- permanent loss of vision
- permanent loss of neurological functions
- death
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