intracranial pressure

Chapter 56 Raised intracranial pressure

What are the major causes of raised intracranial pressure?

What are the pathological intracranial consequences of a head injury?

The brain and spinal cord are enclosed by a rigid compartment, namely the skull and vertebral bodies. Although these bony structures serve to protect the delicate tissues of the central nervous system (CNS), any increase in the volume of the tissues within them is accompanied by an increase in pressure.

Causes of increased intracranial pressure

The pressure of the cerebrospinal fluid (CSF) is normally <15mmHg (lower in children). Table 3.56.1 lists causes of raised intracranial pressure. Many different injuries to the CNS are associated with oedema of the parenchyma. Injury to brain cells causes defects in ion transport, allowing fluid to enter cells, and disruption of the integrity of the blood–brain barrier allows fluid to escape from the blood into the interstitial space. Oedematous brain is soft and the sulci are narrowed.

Table 3.56.1 Causes of raised intracranial pressure

	Type	Examples
Local mass (space-occupying lesion)	Non-neoplastic	Haemorrhage; abscess
	Neoplastic	Primary brain tumour; metastasis
Focal oedema	Surrounding a lesion	Tumour; infarct; abscess
	Surrounding tissue damaged by penetrating trauma	Bullet or shrapnel wounds
Diffuse oedema	Traumatic diffuse neuronal injury	Shaken brain syndrome
	Widespread inflammation	Meningitis; encephalitis; subarachnoid haemorrhage
	Hypoxia	Shock
	Toxic effects	Lead poisoning; some antibiotics
Intracranial congestion	Obstruction to venous outflow	Dural sinus thrombosis
Hydrocephalus (increase in CSF)	Obstruction to CSF flow or prevention of resorption of CSF at arachnoid granulations	Intraventricular haemorrhage; subarachnoid haemorrhage; meningitis
	Increased production of CSF (rare)	Tumour of choroid plexus
Idiopathic		Benign intracranial hypertension