Posts Tagged Intracranial pressure
Crudely speaking, the nervous system is made up of two parts. The peripheral nervous system, composed of nerves and muscles, is rather robust and roams free, exposed to the elements. On the other hand, the central nervous system, consisting of the brain and spinal cord, is delicate and fragile. It is therefore protectively cocooned in a rigid skull and a hardy vertebral skeleton. But even this tough fortress isn’t secure enough for these dainty neurones; they are, after all, the command and control system for the whole body. Therefore, to further insulate them from the physical and physiological perturbations that continuously threaten them, nature has further sequestered them within a very exquisitely regulated irrigation system, the cerebrospinal fluid (CSF).
The CSF is actually a fine filtrate of the blood that flows in the arteries. The sieve is the very forbidding blood-brain barrier (BBB) which turns away all the blood cells, and carefully sets a target on how much protein and glucose to let in. The pressure within the CSF is also very finely tuned, not too high…and not too low; that is how the neurones like it.
Alas, as with all systems, the CSF is vulnerable to external miscreants; infections such as meningitis, encephalitis, and brain abscesses which cause brain swelling or cerebral edema. The CSF is also largely defenceless to internal insurgents, fifth columnists, such as a brain tumours, haematomas (bleeds), and cerebral vein thrombosis (venous clots). The smooth flow of the CSF may also be obstructed, resulting in hydrocephalus or enlargement of the brain’s ventricular system. In all these circumstances, the intracranial pressure is often elevated, a situation aptly dubbed intracranial hypertension. Very often, intracranial hypertension may occur without any obvious cause, and this condition is referred to as idiopathic intracranial hypertension (IIH). Because IIH threatens vision, neurologists have abandoned its old and misleading name, benign intracranial hypertension (BIH).
Intracranial hypertension is no walk in the park as it portends disaster, whatever its cause. As it is a potentially fatal state, the early warning signs are drilled into all doctors in medical school…when their brains are still malleable. These red flag features are severe headache, impaired consciousness, progressive visual loss, dilated or blown pupils, papilledema (swelling of the optic nerve head), and neck stiffness. The standard operating procedure for intracranial hypertension is to deflate the pressure as quickly as possible, by hook or by crook. This may be medical, with infusions such as mannitol, or surgical, with procedures such as decompressive craniectomy (removal of part of the skull). The terminal stage of intracranial hypertension, the most ominous neurological emergency, is cerebral herniation: this is the catastrophic compression of the brainstem into the narrow and tight spinal canal: a physical state that is incompatible with life.
As with all waves, intracranial pressure also has its lows, and it is a no-brainer that neurologists call this intracranial hypotension. This is not as hazardous as intracranial hypertension, but it is worthy of respect in view of its devastating morbidity. The usual cause, and again no prizes for guessing this, is a leak. The puncture in this case is often iatrogenic, in other words, the whodunnit is the doctor. This may be deliberate, such as when the doctor attempts to remove some CSF to test, via a procedure called a lumbar puncture (LP). It may also be accidental, such as when your friendly anaesthetist performs an epidural to relieve pain. In both situations, the dura protecting the CSF is perforated, causing spinal fluid leakage. This manifests as postural or orthostatic headache; by definition, this is a headache that sets in within 15 minutes of standing up, and resolves within 15 minutes of lying down flat. The treatment in such cases is strict bed rest, drinking loads of fluids, including caffeinated drinks, and waiting for the dura to heal itself…usually within one week. If this does not happen, then an intravenous caffeine infusion may be required. An epidural blood patch may also be carried out, again by your friendly anaesthetist, who squirts a little of the victims blood around the site of the leak, to, well, ‘patch it up’. In extremis, surgery may be needed to seal the leak, but this is way beyond my pay grade.
Intracranial hypotension may however develop without any apparent cause, and this is called spontaneous intracranial hypotension (SIH). The causes of SIH include unpredictable dural tears, ruptured meningeal diveticuli (outpouchings of the dura), and direct CSF-venous fistulae (don’t ask!) There are a variety of risk factors for SIH such as connective tissue diseases and bariatric surgery. It is very helpful that SIH leaves characteristic tell-tale clues on brain MRI scans, and these include subdural hygroma (plain fluid collections under the dura); subdural haematoma (blood under the dura); meningeal enhancement with contrast dye; engorgement of the pons and pituitary; and the interesting dinosaur tail sign on fat suppression T2 MRI (FST2WI). The gold standard test to localise the site of leakage in SIH is radionuclide cisternography. In the absence of this rather sophisticated test, a CT myelogram may be considered. Treatment is similar to that of other forms of intracranial hypotension, but other measures that may be required to seal the leak, including the use of fibrin sealeant.
If you have reached the end of this blog post, then you deserve a prize. Four prizes actually: recent interesting reports in the field of SIH to explore:
- The use of transorbital ultrasound in making a diagnosis.
- Treatment of complicated SIH with intrathecal saline infusion.
- SIH complicated by superficial siderosis.
- Severe SIH complicated by sagging brain causing causing postural loss of consciousness.
Increased intracranial pressure is a medical term that refers to growing pressure inside a person’s skull. This pressure can affect the brain if doctors do not treat it.
A sudden increase in the pressure inside a person’s skull is a medical emergency. Left untreated, an increase in the intracranial pressure (ICP) may lead to brain injury, seizure, coma, stroke, or death.
With prompt treatment, it is possible for people with increased ICP to make a full recovery.
In this article, we look at the symptoms, causes, and treatments of increased ICP.
Symptoms of increased ICP
The symptoms of increased ICP can vary depending on a person’s age.
Infants with increased ICP may have different symptoms to older children or adults with the condition, as discussed below.
Symptoms in adults
- pupils that do not respond to light in the usual way
- behavior changes
- reduced alertness
- muscle weakness
- speech or movement difficulties
- blurred vision
As raised ICP progresses, a person may lose consciousness and go into a coma. High ICP may cause brain damage if a person does not receive emergency treatment.
Symptoms in infants
Infants with increased ICP may show some of the same symptoms as adults. In addition, the shape of their heads may be affected.
Infants still have soft plates in their skull that fibrous tissue called skull sutures knit together. Increased ICP may cause the skull sutures to separate and the soft plates to move apart.
Increased ICP in infants may also cause their fontanel to bulge out. The fontanel is the soft spot on the top of the skull.
The following is a list of medical conditions and other causes that can lead to increased ICP:
- brain injury, which is often the result of a blow to the head
- hydrocephalus, or too much cerebrospinal fluid on the brain
- brain swelling
- bleeding or blood pooling in the brain
- brain aneurysm
- brain infection, such as meningitis or encephalitis
- high blood pressure
- brain tumor
- drug interaction
- hypoxemia, a blood oxygen deficiency
In infants, high ICP may be the result of child abuse.
If a person handles a baby or infant too roughly, it may cause them to develop a brain injury. This is known as shaken baby syndrome.
One source has estimated that between 1,000 and 3,000 children in the United States experience shaken baby syndrome each year. The condition may arise if an adult shakes a baby violently to stop them crying.
Anyone who suspects a child may be experiencing abuse can contact the National Child Abuse Hotline anonymously at 1-800-4-A-CHILD (1-800-422-4453).
If a person has the symptoms of increased ICP, they should see a doctor straight away. This is a medical emergency and may lead to brain injury if a person does not receive rapid treatment.
A doctor will measure the ICP in millimeters of mercury (mm/Hg). The normal range is less than 20 mm/Hg. When ICP goes above this, a person may be experiencing increased ICP.
To diagnose increased ICP, a doctor may ask if a person has:
- experienced a blow to a head
- a previous diagnosis of a brain tumor
Then, the doctor may carry out the following tests:
- neurological exam to test a person’s senses, balance, and mental state
- spinal tap that measures cerebrospinal fluid pressure
- CT scan that produces images of the head and brain
After these initial tests, the doctor may use an MRI scan to examine a person’s brain tissue in more detail.
If a person has a diagnosis of increased ICP, a doctor will immediately work to reduce the pressure inside the skull to lessen the risk of brain damage. They will then work to treat the underlying cause of the increased pressure.
Treatment methods for reducing ICP include:
- draining the excess cerebrospinal fluid with a shunt, to reduce pressure on the brain that hydrocephalus has caused
- medication that reduces brain swelling, such as mannitol and hypertonic saline
- surgery, less commonly, to remove a small section of the skull and relieve the pressure
A doctor may give the person a sedative to help reduce anxiety and lower their blood pressure. The person may also need breathing support. The doctor will monitor their vital signs throughout their treatment.
In rare cases, the doctor may put a person with high ICP into a medically induced coma to treat their condition.
Complications of increased ICP include:
- brain damage
Without proper treatment, increased ICP can be fatal.
A sudden increase in ICP is a medical emergency and can be life-threatening. The sooner a person receives treatment, the better their outlook. Many people respond well to treatment, and a person who has experienced increased ICP can make a full recovery.
Preventing increased ICP and its complications
Increased ICP is not always preventable, but it is possible to reduce the risk of some underlying conditions that may lead to increased ICP. We explore how below.
A person can reduce ther risk of stroke by exercising regularly.
Stroke may cause increased ICP. A person can reduce their risk of stroke in the following ways:
- taking steps to lower high blood pressure
- stopping smoking
- managing blood sugar levels
- controlling cholesterol levels
- exercising regularly
High blood pressure
High blood pressure may cause increased ICP. A person can maintain healthy blood pressure by:
- losing weight if overweight or maintaining a healthy weight
- avoiding drugs that increase blood pressure
- eating a healthful, balanced diet
- reducing salt intake
- exercising regularly
A head injury may cause increased ICP. Some examples of how a person can reduce their risk of head injury include:
- avoiding extreme sports or dangerous activities
- always wearing a helmet for activities such as riding a bike
- always wearing a seatbelt when in a car
Increased ICP is when the pressure inside a person’s skull increases. When this happens suddenly, it is a medical emergency. The most common cause of high ICP is a blow to the head.
The main symptoms are headache, confusion, decreased alertness, and nausea. A person’s pupils may not respond to light in the usual way.
A person with increased ICP may need urgent treatment. The immediate aim of treatment is to bring down the pressure on their brain tissue, which helps to reduce the risk of brain damage.
Without proper treatment, this condition may lead to seizure, coma, stroke, or brain damage. In severe cases, increased ICP can be fatal. Rapid treatment may improve a person’s outlook. Making a full recovery with timely treatment is possible.
Increased ICP is not always preventable, but a person can reduce their risk of some causes through lifestyle changes.
Traumatic brain injury can be defined as the most complex disease in the most complex organ. When an acute brain injury occurs, several pathophysiological cascades are triggered, leading to further exacerbation of the primary damage. A number of events potentially occurring after TBI can compromise the availability or utilization of energy substrates in the brain, ultimately leading to brain energy crisis. The frequent occurrence of secondary insults in the acute phase after TBI, such as intracranial hypertension, hypotension, hypoxia, hypercapnia, hyperthermia, seizures, can then increase cerebral damage, and adversely affect outcome. Neuromonitoring techniques provide clinicians and researchers with a mean to detect and reverse those processes that lead to this energy crisis, especially ischemic processes, and have become a critical component of modern neurocritical care. Which is the best way to monitoring the brain after an acute injury has been a matter of debate for decades. This review will discuss how monitoring the injured brain can reduce secondary brain damage and ameliorate outcome after acute brain injury.