11- Paediatric Neurology (2/3) Flashcards
intracranial pressure
‘The pressure within the cranium of the skull’
monroe kellie doctrine
** sum of volumes of (1) Brain, (2 CSF and (3) Intracranial blood is constant**
- Skull is a rigid box
- If one of these components is lost e.g. a bleed or tumour (SOL) , other components of this volume will need to reduce to make sure the sum of volume stays constant
intracranial elastance curve
- As intracranial volume increases initially ICP stays the same due to compensatory mechanisms
- After mechanisms exhausted the ICP will increase
ICP and (1) Blood
Need constant blood supply to supply neurones and brain tissue. Incredibly sensitive to low oxygen.
Cerebral perfusion pressure (CCP) represents cerebral blood flow.
- CPP = Mean arterial pressure (MAP)- ICP
If ICP increased, perfusion of the brain decreases (without cerebral autoregulation)- BV will vasodilate
cerebral autoregulation
- If MAP increases then CPP increases, triggering cerebral autoregulation to maintain cerebral blood flow (vasoconstriction)
- If ICP increases then CPP decreases, triggering cerebral autoregulation to maintain cerebral blood flow (vasodilatation) will result in having to increase MAP- therefore hypertension
- If CPP <50 mmHg then cerebral blood flow cannot be maintained as cerebral arterioles are maximally dilated
- ICP can be maintained at a constant level as an intracranial mass expands, up to a certain point beyond which ICP will rise at a very rapid (exponential) rate
- Damage to the brain can impair or even abolish cerebral autoregulation
ICP and (2) CSF
- CSF produced by the choroid plexus into the lateral ventricles
- Around 500mls produced each day
- Homeostasis, protection, buoyancy and waste clearance
ICP and (3) brain
- If herniating, usually high pressure inside
- Types of herniation
o Subfalcine herniation (commonest)
o Tonsillar herniation (aka coning)
o Uncal herniation
raised ICP is due to
- Too much blood
- Too much CSF
- Too much brain
presentation of RICP
- Headaches (At night time, waking and bending over)
- Nausea + vomiting
- Visual disturbances e.g. double vision
- Drop of >2 in GCS
o Confusion
o Seizures
o Amnesia - Papilledema
- Focal neurological signs
o E.g. CN3 palsy – papillary dilatation - Abnormal posturing (decorticate, decerebrate)
- CushinGs reflex
3 Primary signs of RICP
Cushings triad
- hypertension
- bradycardia
- irregular breathing
LATE SIGNS
pathophysiology of (1) too much blood
1) Too much blood within cerebral vessels (rare)
- Raised arterial pressure- malignant hypertension
- Raised venous pressure- SVC obstruction
2) Too much blood outside the cerebral vessels (haemorrhage)
- Extradural
- Subdural
- Subarachnoid
causes of too much blood within cerebral vessels
- malignant hypertension
- superior vena cava obstruction
Malignant (accelerated) hypertension
- Systolic >180mmHg or Diastolic >120mmHg
* Usually renal cause in children - Signs of target organ damage
o Retinal haemorrhages
o Encephalopathy
o Left ventricular hypertrophy
o Reduced renal function - Urgent referral
Superior vena cava (SVC) obstruction
- Reduction in venous return from head & neck & upper limbs
- Most common cause is malignancy
o Non-Hodgkin’s in children - Oncology Emergency
- Presentation
o Local oedema of the face and upper limbs
o Dilated veins in the arm and neck and anterior chest wall
o SoB
o Difficulty swallowing
o After lifting arms the signs will get worse
(2) Too much CSF also known as
hydrocephalus
hydrocephalus background
- CSF build up abnormally in the brain and spinal cord
- Due to over-production or problems draining or absorbing CSF
hydrocephalus pathophysiology
*- Congenital
- Acquired
- Non-communicating vs communicating
**
hydrocephalus pathophysiology
*- Congenital
- Acquired
- Non-communicating vs communicating
**
congenital hydrocephalus
- Present at birth
- Genetic and non-genetic factors e.g. mutation in L1CAM gene linked to aqueductal stenosis
pathophysiology of congenital hydrocephalus
- Most common cause is aqueductal stenosis ->Insuff drainage of CSF
- Cerebral aqueduct which connect third and fourth ventricle is stenosed
presentation of congenital hydrocephaly
- Enlargement of head circumference- sutures not fused – occipito-frontal circumference (macrocephaly)
Bulging from anterior fontanelles
Poor feeding and vomiting
Poor tone
Sleepiness - Downward gaze
- Delay in neurological development
management of hydrocephalus
- VP shunt- ventricles- peritoneum
- VA shunt- ventricles- atria
Normal CSF Physiology
There are four ventricles in the brain: two lateral ventricles, the third and the fourth ventricles.
The ventricles contain CSF.
The CSF provides a cushion for the brain tissue. CSF is created in the four choroid plexuses (one in each ventricle) and by the walls of the ventricles.
CSF is absorbed into the venous system by the arachnoid granulations.
acquired causes of hydrocephaly
Acquired causes
- Intraventricular haematoma
- Tumour
- Infection
- Trauma
