Notice
Content: Clinical practice
Time: 2:00pm this Thursday
Address: Department of Neurosurgery,
the 8th floor, No.5 Building，
No.1, Hospital.
Neurosurgery
INTRACRANIAL DYNAMICS
The first principle is obvious: the cranial
cavity has a fixed volume that is filled by various
things:
1. Brain tissue
2. CSF
3. Blood vessels and intravascular blood volume
4. Volume associated with any pathologic process,
which can include tumor, cyst, abscess,
hemorrhage, edema, necrosis
A consequence of this principle:
If there is an elevation in the
volume of any one compartment,
there is a stage of compensation in
which the volume of one or more
other compartments can be
reduced to avoid elevations in ICP.
QUESTION: What is Intracranial
Pressure (ICP)?
ICP： the pressure produced by the
content of the cranial cavity (brain tissue,
CSF and blood) on the cranial cavity wall.
Normal ICP：
Adult：0.7～2.0 kPa（70～200mmH2O）。
Child：0.5～1.0kPa（50～100mmH2O）。
The second principle is not
obvious and may seem
counterintuitive:
The spinal fluid is produced at a
constant rate (∼15-20 mL/hr)
largely by the choroid plexus of
the ventricles by an energydependent, physicochemical
process.
The third
basic principle:
The cerebral blood flow (CBF)
normally varies over a wide range
(30-100 mL per 100 g brain tissue
per minute), depending on
metabolic demand from neuronal
activity within a particular area of
the brain.
For any brain region
CBF=Cerebral perfusion pressure/
Cerebral vascular resistance
The fourth
principle:
Injured tissue swells, making obvious the
potential for a cascading injury by a vicious
cycle. If the stage of compensation mentioned
earlier, even with therapy, is exceeded and ICP
is elevated high enough by whatever mechanism
so that cerebral perfusion pressure (CPP)
declines, CBF can decline to levels where tissue
injury occurs.
The vicious cycle. CPP, cerebral perfusion
pressure; ICP, intracranial pressure.
ICP
CPP
Infarction
Edema
Cerebral perfusion pressure (CPP) =
mean systemic arterial pressure
(MAP)-ICP
The fifth principle:
Focal mass effect and its
progression within the complex
anatomy of the cranial cavity.
A sixth
principle:
The separateness of the
phenomenology of the following:
1. Focal mass effect
2. Diffuse raised ICP
3. Ventriculomegaly (enlargement of
the cerebral ventricles)
The pure form of raised ICP
(without focal mass lesion, and
without enlargement of the
ventricular system) is a condition
known as pseudotumor cerebri.
The pure form of ventriculomegaly
is a condition known as normalpressure hydrocephalus (NPH).
Question: What is intracranial
hypertension?
Cranial cavity volume increase, ICP
Increase above 2.0 kPa (200mmH2O),
resulting in a series of corresponding
syndrome.
Causes of intracranial hypertension
1. the content of cranial cavity increase
2. mass effect
3. congential malformation
Clinical manifestations(一）
1. 头痛(headache )： the most common
symptom of intracranial hypertension.
2. 呕吐(vomit )：projectile vomiting
3. 视神经乳头水肿(papilloedema)：
Above three is the typical manifestations of
intracranial hypertension.
Clinical manifestations (二）
4.
disturbance of consciousness and
changes of physical signs
5. others
The diseases caused intracranial
hypertension
1. craniocerebral injury
Acute
subdural
hematoma
Subacute
subdural
hematoma
2. intracranial tumor：
3. intracranial infection ：
intracerebral abscess、
tuberculous meningitis、
tuberculoma of brain。
脑脓肿CT片 intracerebral abscess
Brain
abscess
4. cerebrovascular disease：
cerebral hemorrhage、
subarachnoid hemorrhage。
5. 脑寄生虫病(cerebral parasitosis)：
6.颅脑先天性疾病(congenital disease of
brain)：
7.良性颅内压增高(benign intracranial
hypertension)：
8.脑缺氧(cerebral anoxia)
Influence factors of intracranial
hypertension
1.年龄(Age)：
characteristics of Infants and the elderly
Influence factors of intracranial
hypertension
2.病变扩张的速度(Outstretched velocity of
the disease)：
Influence factors of intracranial
hypertension
3.病变部位(Position of the disease)：
the midline, posterior fossa and filling sinus near
lesions
4.伴发脑水肿的程度(Degree of hydrocephalus ）：
Lesions of the inflammatory response may be
associated with obvious cerebral edema, such as
cerebral abscess
Influence factors of intracranial
hypertension
5.全身情况(General conditions) ：
Liver and kidney function obstacle, and
pulmonary infection, acid-base imbalances
the secondary brain edema
Acute cerebral hernia
Anatomical: the whole cranial
cavity was separated into
three each other mutually
cavity by brain sickle and
cerebellum tent. The cavity
above the cerebellum tent
were divided into control two
cavity, respectively hold about
cerebral hemisphere, The
cavity under the tent
accommodate cerebellum,
bridge brain and the medulla
oblongata.
The causes of the formation of
cerebral hernia
When a certain cavity has
the intracranial lesions, this
cavity pressure is greater
than adjacent cavity pressure,
and brain from high to low
pressure area shift and lead
to brain tissue, vascular and
cranial nerves, and other
important structure
compression and shift,
resulting in a series of serious
clinical symptoms and signs,
called "the cerebral hernia".
Brain herniation
1. infrafalx cerebri
herniation
2. transtentorial
herniation
3. Foramen magnum
herniation
Management of cerebral hernia
Principle of management
1. Rapid intravenous input permeability liquid, reduce
intracranial pressure to alleviate temporarily condition.
Commonly used medicines for mannitol 125 ~ 20% 250ml rapid
static drops.
2. Early clear lesions properties and parts, seasonable purify for.
3. Causes difficult to express or lack of effective healer, can choose
some palliative operation to alleviate increase intracranial
pressure. Such as hydrocephalus can choose ventricle external
drainage, cerebrospinal fluid diversion decompression, The
cerebellum curtain cut trace hernia feasible temporal
component decompression, Foramen magnum hernia feasible
suboccipital decompression.
Summary
1、the content of the cranial cavity
2、ICP,ICP value
3、 the vicious cycle of ICP and CPP
4、the relation between CBF 、CPP and CVR
5、the relation between CPP 、 ICP and MAP 6、
Intracranial hypertension
7、Clinical manifestations of Intracranial
hypertension
8、pseudotumor cerebri
9、brain herniation