OVERVIEW: What every practitioner needs to know

Are you sure your patient has increased intracranial pressure? What are the typical findings for this disease?

Increased intracranial pressure (ICP) is a life threatening emergency that requires prompt recognition and management. Increased ICP can be due to both neurological and non-neurological illness, and symptoms may vary by age group.

The most common cause of increased ICP is traumatic brain injury – other causes include infection, stroke, hydrocephalus, ventricular shunt malfunction, arachnoid cysts, tumors, craniosysnostosis syndromes and idiopathic intracranial hypertension.

Children with increased ICP require prompt referral and transfer to a pediatric intensive care unit, with neurosurgical consultation and support. Management of increased ICP consists of general principles of stabilization of airway, breathing and circulation, as well as specific measures to reduce increased ICP and promote cerebral perfusion with controlled ventilation, hyperosmolar therapy, sedation and in certain instances, surgical interventions such as drainage of cerebrospinal fluid (CSF) and decompressive craniectomy. Aggressive management of increased ICP can improve survival and neurological outcomes.

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Normal ICP varies with age, and values are not well established for children. Normal ICP values are less than 10 – 15 mmHg for older children, less than 3 – 7 mmHg for younger children and less than 1.5 – 6 mmHg in term infants. ICP values greater than 20 – 25 mmHg are considered to be increased and require treatment in most instances. ICP values greater than 40 mmHg indicate severe life-threatening intracranial hypertension and represent a life threatening emergency. In the case of preterm infants, normal ICP values average around 3 mmHg, with values greater than 7 mmHg indicating intracranial hypertension.

Symptoms and signs of increased ICP vary by age (due to the presence or absence of an open fontanelle) and severity of increase in ICP (see Table I; also see Figure 1, Figure 2, Figure 3, Figure 4 and Figure 5).

Figure 1.

Abducens palsy

Figure 2.

Papilledema

Figure 3.

Normal optic disc

Figure 4.

Bulging fontanelle

Figure 5.

Hydrocephalus with enlarged head circumference

Table I.
Age Group Mild to moderate increase in ICP Severe increase in ICP
Toddlers and school age children Symptoms of headache, vomiting, diplopia, lethargy or irritability. Signs of an abducens palsy, abnormal pupillary reactions and papilledema.
Symptoms of reduced level of consciousness and posturing. Signs of unilateral or bilateral dilated, poorly reactive pupils; reduced level of consciousness and Cushing’s triad
Neonates and infants Symptoms of inconsolable crying, vomiting, lethargy or irritability. Symptoms of reduced level of consciousness and posturing.
Signs of bulging fontanelle, widened sutures, persistent downward eye deviation and increased head circumference. Signs of unilateral or bilateral dilated, poorly reactive pupils; reduced level of consciousness and Cushing’s triad

Additionally, the location of intracranial lesions that result in increased ICP may be associated with specific neurological signs and herniation syndromes. Focal neurological deficits associated with increased ICP may result in contralateral hemiparesis from supratentorial lesions and ataxia, head tilt and meningismus from infratentorial lesions (see Table II; also see Figure 6).

Table II.
Location Type of herniation Clinical Features
Supratentorial 1. Lateral descending transtentorial (downward and medial herniation of uncus and parahippocampal gyrus due to mass effect in the cerebrum).  Impaired consciousness, abnormal respirations, third nerve palsy (ipsilateral dilated pupil, ptosis), contralateral hemiparesis and sometimes ipsilateral hemiparesis (due to Kernohan’s notch).
  2. Central descending transtentorial (downward herniation of the cerebral hemispheres due to mass effect in the supratentorial region).  Impaired consciousness, abnormal respirations, symmetrical small reactive or mid-position fixed reactive pupils, decorticate evolving to decerebrate posturing.
  3. Subfalcine herniation (medial herniation of the cingulate gyrus under the falx). Headache, impaired consciousness, monoparesis of the contralateral lower extremity.
  4. Transcalvarial (herniation through skull bone defect either as a result of trauma or surgery). Variable depending on region of brain affected, may also be asymptomatic.
Infratentorial 5. Upward transtentorial (upward herniation of the cerebellar vermis and midbrain due to mass effect in the posterior fossa). Ataxia, head tilt, meningismus, downward gaze deviation, upgaze palsy, nausea, vomiting, decerebrate posturing.
  6. Transforaminal (downward herniation of cerebellar tonsils and medulla via the Foramen magnum). Impaired consciousness, meningismus, ophisthotonus, vomiting, Cushing’s reflex (systemic hypertension, bradycardia and periodic breathing), decerebrate posturing, apnea.
Figure 6.

Brain herniation syndromes

Measurement of Intracranial Pressure

ICP is the pressure exerted by the contents of the brain, blood and CSF in the cranial vault. By convention, ICP is supratentorial CSF pressure measured either in the lateral ventricles or cerebral cortex and usually expressed as mmHg. A variety of techniques are available to measure ICP, including ventricular cannulation and intraparenchymal devices. Other devices such as epidural and subdural devices are not typically used in children nowadays.

Ventricular cannulation

This technique consists of placement of a ventricular catheter via a burr hole into a lateral ventricle. CSF pressure can be measured using a transducer.

Advantages:

  • This device enables CSF drainage as a therapeutic measure when ICP rises.

  • CSF samples can be sent for laboratory analysis if needed.

  • Antibiotics can be administered intra-thecally.

  • Simultaneous measurement and drainage of ICP is possible with newer devices

Disadvantages:

  • CSF leakage and /or catheter displacement could result in false low readings.

  • The risk of infection increases after 72 hours.

  • Placement in the ventricle might be difficult if the ventricles are collapsed due to severe cerebral edema.

  • Vigilant nursing care is required to monitor CSF output to prevent overdrainage, especially with changes in patient position.

Intraparenchymal devices

This technique consists of placement of the catheter via a burr hole 1-2 cm into the substance of the brain parenchyma or a lateral ventricle. Typically, the catheter is placed in the nondominant frontal white matter in the case of diffuse brain injury, or in the percontusional area in the case of focal brain injury. CSF pressure can be measured using a transducer.

Advantages:

  • This device is easy to place and easy to maintain.

  • This device is associated with lower risk of infection and hemorrhage.

  • There is no risk of overdrainage with this device.

  • Modifications of such devices can be used for measurement of brain tissue oxygenation (Licox) and measurements of chemicals using microdialysis techniques.

Disadvantages:

  • This device cannot be used to drain CSF as a therapeutic measure.

  • The device may require re-zeroing or replacement if ICP starts drifting over time.

Placement of both types of devices requires careful detail to platelet count and coagulation profile in patients. These devices need to be placed under sterile and aseptic conditions. Sedation and analgesia is required for placement of these invasive devices.

These devices should be removed once ICP normalizes or stabilizes. Typically following traumatic brain injury, ICP peaks around 3 days after injury, though sometimes the peak is delayed up to 7 days after injury. The benefits of continued ICP monitoring thereafter are outweighed by the risks of infection, hemorrhage and accidental dislodgement of the device.

Non-invasive measurements of ICP

Recently, tympanic membrane displacement and optic nerve sheath diameter measurement have emerged as two techniques that can potentially measure ICP non-invasively. In addition to being safer, these techniques can also be cost-effective and carried out repetitively without the need for additional sedation. Both these techniques require further validation before they can be recommended for widespread use.

The normal ICP waveform contains three components reflecting the cardiac cycle (See Figure 7).

The abnormal ICP waveform reflects decrease in cerebral compliance (See Figure 8).

Figure 8.

Abnormal ICP waveform

Causes of Increased Intracranial Pressure

Increased ICP is usually due to an increase in brain volume, blood volume or CSF volume or a combination thereof based on the Monroe-Kellie doctrine (see Table III).

Table III.
Increase in brain volume    
  Intracranial space occupying lesion  
    Tumor (primary, metastases)
    Abcess (primary, embolic)
    Hematoma
    Vascular malformation
  Cerebral edema  
    Trauma
    Hypoxia-ischemia
    Infection (meningitis, encephalitis)
    Stroke
    Hepatic encephalopathy
    Diabetic ketoacidosis
    Malignant hypertension
    High altitude sickness
    Inborn errors of metabolism
    Dialysis dysequilibrium syndrome
    Vasculitis
    Hyponatremia
  Skull bone abnormalities  
    Craniosynostosis syndromes
    Mucopolysaccharidoses
 Increase in CSF    
    Obstructive hydrocephalus
    CSF secreting tumor
     Idiopathic intracranial hypertension
    Arachnoid cyst
    Ventricular shunt malfunction
 Increase in blood    
    Vascular malformation
    Stroke

What other disease/condition shares some of these symptoms?

Diseases/conditions that can mimic symptoms/signs of increased intracranial pressure include:

  • Migraine

  • Seizure

  • Coma

  • Intoxication

  • Megalencephaly

  • Deformational plagiocephaly

  • Optic neuritis

  • Hypertrophic pyloric stenosis

  • Intestinal obstruction (intussuception, volvulus)

  • Esotropia due to syndromes (Mobius, Duane)

What caused this disease to develop at this time?

Increased intracranial pressure can be explained on the basis of the Monroe-Kellie doctrine. Usually, in response to increase in intracranial volume, initial compensation to maintain normal cerebral perfusion and ICP occurs. This consists of displacement of CSF from the ventricular space and the cerebral subarachnoid space to the spinal subarachnoid space along with increased absorption of CSF followed by decreased production of CSF. Infants with open fontanelles and sutures may be able to compensate better, but are still susceptible to elevations in ICP. Eventually, these compensatory mechanisms are overwhelmed resulting in a steep increase in ICP (See Figure 9).

Normal brain metabolism is dependent on adequate cerebral blood flow. Cerebral perfusion pressure (CPP) is the pressure at which the brain is perfused and is an indicator of adequacy of cerebral blood flow. CPP is expressed as the difference between mean arterial pressure (MAP) and ICP. Normal CPP values vary with age and are not well-defined for children. However, most experts agree that children should have a CPP > 50-60 mmHg, and infants/toddlers should have a CPP > 40-50 mmHg. Typically, cerebral blood flow is maintained at a constant via the phenomenon of autoregulation across a wide range of CPP from 50-160 mmHg (See Figure 10). The autoregulation curve is shifted to the left in the case of neonates and younger children, while chronic hypertension results in shifting of the curve to the right.

Figure 10.

Autoregulation of cerebral perfusion pressure

Other important variables that affect cerebral blood flow include changes in blood oxygen and carbon dioxide tension. Typically, cerebral blood flow remains constant until blood oxygen tension falls below 50 mmHg. Thereafter, cerebral blood flow increases as blood oxygen tension continues to fall (See Figure 11). A linear relationship exists between cerebral blood flow and blood carbon dioxide tension between 20 mmHg and 80 mmHg, In this range, as blood carbon dioxide tension rises, cerebral blood flow increases as well. Thus, at a blood carbon dioxide tension of 80 mmHg, cerebral blood flow is double the normal value. Conversely, at a blood carbon dioxide tension of 20 mmHg, cerebral blood flow is almost halved (See Figure 12).

Figure 11.

Blood oxygen tension and cerebral blood flow

Figure 12.

Blood carbon dioxide tension and cerebral blood flow

When intracranial volume increases, initial compensatory mechanisms prevent a rise in ICP and through the process of autoregulation maintain adequate CPP with cerebral blood flow. With further increase in ICP, autoregulation is overwhelmed and CPP starts falling. CPP < 40 mmHg is a significant predictor of mortality in children with traumatic brain injury. CPP and cerebral blood flow can be increased by increasing MAP, reducing ICP or through a combination of both approaches.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

A lumbar puncture is helpful to measure CSF pressure and obtain other studies on CSF including clinical chemistry and microbiological tests. Strictly speaking, lumbar puncture measures neuraxis CSF pressure, in the form of the opening pressure using a fluid column which correlates reasonably well with ICP. Opening pressure is usually expressed as cm of H2O and can be converted to mmHg by dividing by a factor of 13.9. Such measurements can be confounded by the application of sedation as well as the position of the child during the lumbar puncture.

When an intracranial mass is suspected, lumbar puncture is absolutely contraindicated till further confirmation with computerized tomography (CT) or magnetic resonance imaging (MRI) and a neurosurgeon should be consulted for measurement of ICP.

When should one suspect an intracranial mass?

  • Altered mental status

  • Focal neurological deficits, including focal seizures

  • Papilledema

Other studies such as glucose (diabetic ketoacidosis), electrolytes (diabetic ketoacidosis, hyponatremia), blood gas analysis (diabetic ketoacidosis, inborn errors of metabolism), liver functions (hepatic encephalopathy), markers of autoimmune disorders (vasculitides) and microbial cultures (infections) may be useful for diagnosis of underlying disorders associated with increased ICP.

Would imaging studies be helpful? If so, which ones?

Historically, skull radiographs were used to assess chronically increased ICP through the appearance of “copper beating” with separation of sutures and erosion of the clinoid process (See Figure 13). However, the utility of skull radiographs was limited in settings of acutely increased ICP.

“Newer modalities”, such as computerized tomography (CT), magnetic resonance imaging (MRI), angiography, and ultrasonography (US), are much more useful to diagnose underlying intracranial causes of increased ICP, but may be of limited value in assessing the degree of increase in ICP itself.

Figure 13.

Copper beaten skull

1. Computerized tomography (CT) of the brain

Findings can range from:

  • enlarged ventricular system

  • transependymal flow of CSF

  • obliteration of basal cisterns and sulci

  • evidence of herniation

  • specific lesions (tumors, hemorrhage, infections, abnormalities of skull bones) with midline shift and mass effect

  • generalized cerebral edema with loss of gray-white differentiation

  • cervical spine abnormalities

  • skull fractures and pneumocephaly (in the case of trauma)

Advantages – easy to obtain (quick study, can avoid sedation), less expensive

Disadvantages – insensitive to image the posterior fossa, higher risk of radiation exposure (can be minimized using dose specific pediatric protocols), especially if serial imaging is required. (One pediatric dose adjusted head CT = approx 300 chest radiographs)

2. Magnetic resonance imaging (MRI) of the brain

Findings can range from

  • changes seen on CT

  • findings of diffuse axonal injury (DAI)

  • detection of microhemorrhages

  • Increase in optic nerve sheath diameter

Advantages – greater detail, better prognostication of neurocognitive outcomes, no risk of radiation, superior to image posterior fossa lesions

Disadvantages – difficult to obtain in non-cooperative patients with greater risks (long study, risk of sedation in the setting of CE), more expensive

3. Angiography (including CT and MR angiography)

Findings can range from

  • arteriovenous malformations

  • dissection of blood vessels

  • aneurysmal bleeds

4. Ultrasonography – useful when the fontanelle is open

Findings can range from

  • intraventricular hemorrhage

  • enlarged ventricular system

  • subdural hemorrhage

  • intraparenchymal hemorrhage

Other less commonly used modalities include transcranial doppler ultrasound, positron emission tomography (PET), near infra-red spectroscopy (NIRS) and visual evoked potentials (VEP).

Confirming the diagnosis

The Brain Trauma Foundation published guidelines developed by experts in pediatric traumatic brain injury in 2012 that are helpful to diagnose, monitor and manage increased ICP in the setting of traumatic brain injury. These guidelines are freely available at the Brain Trauma Foundation website (www.braintrauma.org). These guidelines often reflect expert opinion due to the lack of pediatric studies.

If you are able to confirm that the patient has increased intracranial pressure, what treatment should be initiated?

Children with suspected or confirmed increase in ICP should be promptly referred and transferred to a pediatric intensive care unit preferably with pediatric neurosurgical capabilities. The goals for treatment of increased ICP include avoidance of hypoxia and maintenance of cerebral perfusion. Treatment of increased ICP in the context of traumatic brain injury consists of both first-tier and second-tier therapies as outlined in the following figures. This outline can be adapted for management of increased ICP in the setting of other etiologies.

First-tier therapies consist of careful attention to the ABCs (including securing the airway, maintaining normal ventilation and adequate perfusion with careful management of blood pressure), elevation of the head to 30 degrees, sedation and analgesia, drainage of CSF, neuromuscular blockade and hyperosmolar therapy (mannitol or hypertonic saline) (See Figure 14).

Figure 14.

First-tier therapies for increased ICP

Second-tier therapies should be considered when first-tier therapies are ineffective and include lumbar CSF drainage, decompressive craniectomy, controlled hyperventilation, high-dose barbiturate therapy and moderate hypothermia (32-34 C) (See Figure 15).

Figure 15.

Second-tier therapies for increased ICP

Additionally, treatment should be directed to the underlying etiology of increased ICP. For example, surgery may be indicated for resection of tumors and vascular malformations, drainage of abscesses and blood collections, shunting of hydrocephalus and correction of craniosynostosis abnormalities. Similarly, aggressive medical management may be necessary for diabetic ketoacidosis, hepatic encephalopathy, inborn errors of metabolism and malignant hypertension.

Medications such as acetazolamide and other diuretics may be considered in the context of chronically increased ICP to reduce CSF production. Steroids may be useful to reduce ICP in the setting of vasogenic edema associated with brain tumors and inflammatory processes such as tuberculous meningitis and vasculitides.

What are the adverse effects associated with each treatment option?

First-tier therapies and adverse effects:

  • Elevation of the head to 30 degrees: This may be associated with reduced cerebral perfusion in some instances. Additionally, with head elevation, every effort should be made to keep the head midline and avoid falls from the bed.

  • Sedation and analgesia: Adverse effects may include oversedation and cardiorespiratory compromise. Depending on the agent(s) used, other effects may include immunocompromise and endocrine dysfunction.

  • Drainage of CSF: This may be associated with overdrainage especially with changes in position, dislodgement of the catheter and infectious complications.

  • Neuromuscular blockade: This practice can result in critical illness myopathy and persistent weakness in survivors.

  • Hyperosmolar therapy: The use of mannitol may be associated with the development of hypovolemia from brisk diuresis with resulting hypotension and hypoperfusion of the brain parenchyma. Hypertonic saline solutions may result in thrombophlebitis especially when infused via peripheral venous catheters.

Second-tier therapies and adverse effects:

  • Lumbar CSF drainage: This may be associated with overdrainage especially with changes in position, dislodgement of the catheter and infectious complications.

  • Decompressive craniectomy: This approach may result in uncontrolled bleeding, herniation, and infectious complications.

  • Hyperventilation: This therapy can result in reduced cerebral blood flow and reduced cerebral perfusion with worsening of cerebral injury.

  • High-dose barbiturate therapy: Adverse effects may include oversedation and cardiorespiratory compromise. Other effects may include immunocompromise and endocrine dysfunction.

  • Moderate hypothermia: This practice needs to be performed in centers that are capable of induced hypothermia. Adverse effects include coagulopathy, arrhythmias, hyperglycemia, electrolyte abnormalities and increased risk of infections.

Medications such as acetazolamide and other diuretics may be associated with acidosis and resulting cardiac disturbances as well as hypovolemia. Steroids have numerous adverse effects including hypertension, hyperglycemia, impaired wound healing, immunodeficiency, and bone demineralization.

What are the possible outcomes of increased intracranial pressure?

The outcome of raised ICP depends on the underlying etiology and extent and duration of increase in ICP. For example, acute increase in ICP related to shunt malfunctions may be easily reversed with minimal consequences. In contrast, increase in ICP associated with severe traumatic brain injury that is resistant to all therapies is usually associated with very poor outcomes. Chronically increased ICP may result in gradual loss of neurological function which may be partially reversible with control of increased ICP.

The first-tier therapeutic options to treat increased ICP have a more favorable risk/benefit ratio compared with the second tier therapies. Second-tier therapies require institutions and personnel capable of undertaking these approaches.

What complications might you expect from the disease or treatment of the disease?

Increased ICP can result in a wide range of complications depending on the extent of increase in ICP and rapidity of increase in ICP. Complications include visual loss, cerebral atrophy with cognitive decline and loss of milestones, altered mental status and death. Treatment of increased ICP is associated with risks and should be undertaken by experienced providers with adequate institutional capabilities.

How can increased intracranial pressure be prevented?

Prevention of increased ICP is best achieved by early recognition and management of disease processes that are associated with the development of increased ICP. Additionally, public health measures to minimize traumatic brain injury and popularize the recognition of common conditions associated with increased ICP are highly important.

What is the evidence?

Sankhyan, N, Vykunta Raju, KN, Sharma, S, Gulati, S. “Management of raised intracranial pressure”. Indian J Pediatr. vol. 77. 2010. pp. 1409-16.

Singhi, SC, Tiwari, L. “Management of intracranial hypertension”. Indian J Pediatr. vol. 76. 2009. pp. 519-29.

“Guidelines for the acute medical management of severe traumatic brain injury in infants, children and adolescents”. Pediatr Crit Care Med. vol. 13. 2012. pp. S1-S82.

Ongoing controversies regarding etiology, diagnosis, treatment

Controversies regarding definition of increased ICP in children:

  • What is the exact threshold of increased ICP and how does this vary by age?

  • What is the best modality for diagnosis of increased ICP?

Controversies regarding treatment of increased ICP in children:

  • How much increase in ICP is too much increase?

  • Should increase in ICP or decrease in CPP be targeted?

  • How should the different modalities for treatment of increased ICP be used?

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