Why is an increased ICP an emergency
The contents of our skull and dura can be divided into three main compartments: brain parenchyma (which occupies a volume of approximately 1.4 L), spinal fluid (52-160 mL), and blood (150 mL). An increase in any of these three compartments, as per the Monro-Kellie hypothesis, will occur at the expense of the remaining two. In addition, intracranial compliance has been noted to decrease with rising pressure, thus causing further compromise in cerebral perfusion. The normal range of ICP has been reported to be 5 to 15 mm Hg.
*Bethesda Handbook of Oncology
Causes
In patients with cancer, volume changes in brain parenchyma can be the result of:
- primary or secondary brain tumors +/− intratumoral hemorrhage
- vasogenic (peritumoral) or cytotoxic (in the setting of cytotoxic chemotherapy) edema
- extra-axial mass lesions (dural tumors, infection, or hemorrhage)
- indirect neurologic complications.
Brain metastases are, in fact, the most common cause of increased ICP in this population. Lung cancer and melanoma, specifically, are most commonly associated with central nervous system (CNS) metastasis.
An imbalance between cerebral spinal fluid (CSF) production and reabsorption may also contribute to increased ICP:
- subependymal giant cell astrocytoma
- lymphoma
- choroid plexus papilloma
- ependymoma
- meningioma
*Bethesda Handbook of Oncology
Clinical
- Altered Mental State
- Coma
- Confusion
- Headache
- Worse in the mornings
- Improvement with emesis
*Bethesda Handbook of Oncology
- Focal Signs
- Papilledema (late sign)
- chronic disturbance of spinal fluid reabsorption can present with a triad of :
- cognitive decline, incontinence, and ataxic gait
- Hyponatremia secondary to SIADH
*Bethesda Handbook of Oncology
Diagnosis
- History
- Physical
- CT
- MRI with with gadolinium
- Imaging prior to doing LP if required for diagnostic work-up
*Bethesda Handbook of Oncology
Treatment
- Elevated head of the bed 30 degrees
- Tylenol if pyrexial
- maintenance of high normal serum osmolality with osmotic diuresis
- most commonly used hyperosmolar agent used is 20% to 25% mannitol solution given at 0.75 to 1 g/kg body weight followed by 0.25 to 0.5 g/kg body weight every 3 to 6 hours
- moderate to high dose dexamethasone (6-10 mg every 6 hours up to 100 mg/d) can be effective in patients with vasogenic edema, they should be avoided in patients suspected to have CNS lymphoma prior to tissue diagnosis
- Mechanical hyperventilation aiming for PCO2 25 – 30mmHg
- Anti-epileptics
- crucial to treat the underlying disease process, whether that includes
- surgical resection/decompression,
- systemic/intrathecal chemotherapy, and/or
- whole brain irradiation.
*Bethesda Handbook of Oncology
