Neurosurgery

Neurosurgery

HEAD INJURY

Introduction

Head trauma results in approximately 70,000 deaths, 80,000 long-term disabilities, and 60,000 new seizure disorders each year

These injuries most often occur in individuals who are 15-24 years old and are twice as common in men

Causality is bimodal

• vehicular accidents being most common in those under 25 years
• falls in those over 75 years

Nearly half involve intoxication with drugs or alcohol

Anatomy

Scalp

• Skin
• Connective tissue layer
• Aponeurotic layer-frontalis, occipitalis and temporalis merge
• Pericranium
• Blood supply
  
  • ECA and ICA
  • Vessels run in dense connective tissue so bleed profusely when cut(can’t retract)
  
  

Structure of the brain

Forebrain	Midbrain	Hindbrain
Cerebrum 2 cerebral hemispheres connected by corpus collosum Cerebral hemispheres have central cavities called the lateral ventricles Gyri and sulci Diencephalon Thalamus Hypothalamus Third ventricle (communicates with the lateral ventricles through the interventricular foramina)	Cerebral peduncles (consists of descending tracts from the cerebrum to the spinal cord) Crus cerebri Substantia nigra tegmentum Tectum 4 colliculi Pineal body	-Pons -Medulla oblongata -Cerebellum

Meninges

Dura mater	Arachnoid mater	Pia Mater
Falx cerebri Tentorium cerebelli Extradural space- seperates dura from the skull meningeal vessels run in this contains venous sinuses Subdural space- seperates arachnoid from dura	Arachnoid villi project into dural  sinuses Subarachnoid space-contains CSF-is  traversed by cranial nerves,arteries  and veins	Invests brain and SC tissue

Blood supply

Venous drainage

CSF

• Produced in the choroid plexus of the lateral 3rd and 4th ventricles
• Flow is from the lateral to the 3rd to the 4th ventricle via cerebral aqueduct
• Then flows into subarachnoid space via 2 foramen of Luschka and the single foramen of magendie
• Absorbed back into the blood stream via the arachnoid villi which project into the sagittal sinus
• 140mls contained in adult
• 500ml/day produced

Neurophysiology

Blood brain barrier

• Selectively controls entry of  substances into the ECF of the CNS
• Consists of endothelial cells with  tight junctions
• Active mechanisms exist to transport  substances
• May be compromised in cases of  severely raised intracranial pressure

Intracranialpressure

• Normal ICP=10mmHg
• Abnormal>20 mmHg
• Monroe Kellie doctrine states
  
  • the cranial compartment is incompressible
  • the volume inside the cranium is a fixed volume
  • its constituents namely blood, CSF, and brain tissue create a state of volume equilibrium
  • any increase in volume of one of the cranial constituents must be compensated by a decrease in volume of another.
  • Compensation occurs up to a value of 100mls. eg. an increase in lesion volume (e.g. extradural hematoma) will be compensated by thedownward displacement of CSF and venous blood.
  
  

Why is ICP important

• Cerebral perfusion pressure(CPP)= mean arterial pressure(MAP)-ICP
• MAP=1/3 pulse pressure+diastolic blood pressure
• Thus decreasing ICP or increasing MAP leads to an increase in CPP
• CPP is normally controlled by auto regulation with arteriolor vasoconstriction keeping a constant value between 50 and 1500mmHg.
• If this fails as in pathological states this can lead to a significant drop in CPP

Causes of raised ICP

Surgical

• Haematoma
• Oedema due to contusion/haematoma
• Oedema due to ischaemia
• Infection-empyema

Medical

• Electrolyte imbalance
• Ischaemia-CVA
• Infection-meningitis

Effects of raised ICP

• Tentorial herniation
• Pupillary dilatation due to compression of 3rd CN
• Motor weakness due to compression of corticospinal tract
• Coning-brainstem is being squeezed through the foramen magnum compressing cardiorespiratory centres

Presentations of Raised ICP

Decreased conscious level

Headache

Nausea and vomiting

Fall in GCS

Dilated pupil

Papilloedema

Neurological assessment  in A&E

Always commence with

Airway

Breathing

Circulation

Disability             

• Neurological status
• Pupils- size, symmetry, response to light
• AVPU score- Alert, Verbal stimuli, Pain, Responsive

Secondary Survey of the  head

Neurological state- GCS, Pupils, Eyes

Examination of the face- Facial bones, Teeth

Examination of the scalp

• Battle’s sign-fracture of the base of  the skull
• CSF/blood from ears
• Presence of scalp wound/haematoma

Classification of head  injury

GCS

• Minor-GCS>8
• Major-GCS<8

Mechanism

• Blunt
• Penetrating

Pathology

• Focal/Diffuse
• Primary/Secondary

Intracranial haemorrhage

Classification

Contusion

• Classed under focal brain injury
• Due to rapid deceleration injuries
• The brain hits off the rigid skull  causing coup and contre coup  bruising
• Coup injury  occurs under the site  of impact with an object
• Contrecoup injury  occurs on the  side opposite the area that was  impacted
• Frontal and temporal contusions  are common
• Also cause mass effect as a result  of blood and oedema which leads  to midline shift

Extradural haematoma

• Due to trauma-blow to temporal or  parietal bone
• Causes rupture of underlying  middle meningeal artery
• Presents as initial concussion  followed by lucid interval  due to  accommodation of expanding  haematoma.
• Followed by rapid decompensation  as ICP raises when the temporal  lobe is pushed into the tentorial  opening.
• This is called coning.
• Carries a 5% to 20% mortality  rate.
• Respects the suture lines. Seen on CT Brain as lens-shaped blood collectionwith a convex medial border .

Subdural haematoma

• Severe head injury-Sudden deceleration injuries --leads to a more rapid deterioration in patient’s condition.
• Due to rupture of a bridging vein due to  shearing forces or laceration of brain substance
• Thin layer of blood in the subdural space (between the dura and arachnoid mater)
• Appear on Ct Brain as crescent-shaped blood collections with a concave medial border. This does not resect the suture lines. Note also midline shift.

Subarachnoid haemorrhage

• Trauma is the most common cause of Subarachnoid haemorrhage
• Bleeding occurs between the arachnoid and pia mater.. SAH may be complicated by hydrocephalus.
• Confusion can sometimes arise between SAH due to trauma and due to a ruptured aneurysm or arteriovenous malformation (AVM); the patient may collapse and hit their head as a result of a bleed and the history (from the patient or a witness) is important.
• Increased attenuation is seen in the CSF spaces over the cerebral hemispheres  (look closely at the Sylvian fissure), in the basal cisterns or in the ventricular system. It may be complicated further by Hydrocephalus

Intracerebral haemorrhage

• Injury of the brain substance itself
• Associated with cerebral  laceration, contusion, oedema and  necrosis
• Evacuation of the clots can have  poor results
• Not as easy to remedy.

Diffuse axonal injury

• Occurs due to shearing forces  between grey and white matter.
• Generalized cerebral oedema  results due to parenchymal  disruption leadsing to an increase  in ICP
• Ranges from
  
  • mild form-concussion
  • severe form- persistent vegetative  state
  
  

Monitoring of ICP

Invasive

• External ventricular drain(EVD)- inserted via frontal Burr hole into lateral ventricles. This allows drainage of CSF if necessary
• Brain parenchymal ICP transducer- catheter is introduced through Burr hole and placed in contact with parenchyma and linked to pressure transducer

Non- invasive

• Transcranial pressure-estimates flow in middle meningeal artery.

Medical management of  raised ICP

Sedate and intubate

Nurse patient at 30 degree angle- aids venous drainage

Mild hyperventilation- keep pCO2  approx 4.5kPa- if allowed to fall  lower this leads to vasoconstriction  and subsequent ischaemia

Mild hypothermia

Maintain ICP at 10 mmHg

• Mannitol(0.5g/kg)- transient mild reduction in ICP
• Hyperventilation
• Hypothermia
• Thiopentone infusion(5mg/kg)

Aim to maintain CPP at 60-70mmHg

• Fluid management
• Use of inotropes(this increases MAP)

Surgical management

External ventricular drainage-drain  CSF to transiently reduce ICP

Burr holes

Evacuation of mass lesion +/-  craniectomy

Decompressive craniectomy

Surgical management

Burr Holes

• Small holes through the skull over the site of an intracranial haematoma
• Aim is for partial evacuation and reduction in ICP
• Must be placed directly over haematoma
• Temporary measure only whilst awaiting definitive neurosurgical intervention
• Also used for insertion of invasive monitoring equipment
• Surgical management

Decompressive craniectomy

• part of the skull is removed to allow  the brain room to expand
• some evidence suggests that it does  improve outcome by lowering ICP
• The part of the skull that is removed  is known as a bone flap

BRAIN TUMOUR

Clinical Presentation

Headache of raised ICP 55%

Seizures 25%

Progressive Focal Neurodeficits:              70%

• Motor
• Sensory/Speech
• Cerebellar symptoms!
• CrN-??
• Leptomeningeal spread

Progressive Global Neurodeficits: Frontal-temporal

• Hydrocephalus
• Leptomeningeal spread

Stroke: Intratumoural bleed (15%)

• Renal
• Choriocarcinoma
• Thyroid

History - progressive

Headache

• Early morning  ???  Hypoventilation during sleep, coughing, straining,  bending
• Associated nausea and  vomiting (40%)

Red flags

• Systemic symptoms – mitotic  lesion  - wt loss, appetite,
• PHx cancer
• PHx radiation exposure
• Certain family histories – Von  Hippal Lindau,  Neurofibromatosis

Clinical exam

Neurological exam

Look for other secondary  deposits

Look for primary

Investigations

• CT
• MRI
• CXR
• CT abdomen/thorax

Primary glial brain tumours

Grading and survival: astrocytic gliomas

Metastasis

Metastases to the brain greatly outnumber primary tumors

Virtually any primary cancer may spread to the CNS:

• brain
• spinal cord
• leptomeninges
• dura
• pituitary gland

Sources of brain mets in adults

lung cancer                >40%

breast                            40%

renal cell              7%

GI                            6%

melanoma              3%

Undetermined 4%

Meningioma

Extra-axial (outside the arachnoid)

Primarily a surgical disease

Usually classified by location

For residual or recurrent meningioma use radiation and/or focused radiation

Vestibular schwannoma

Arise from vestibular branch of CN VIII

Present with slowly progressive hearing loss

Bilateral in NF2

Treated options surgery or focused radiation (e.g. Gamma Knife), observation (elderly)

Pituitary adenomas

Non-functioning (present with visual symptoms, headache, hypopituitarism)

Functioning:

              prolactin (galactorrhea,               infertility)

              growth hormone (Acromegaly)             

              ACTH (Cushing’s syndrome)

Rarely pituitary apoplexy

Treated with drugs, surgery, radiation

Primary CNS Lymphoma

Most common in immune-suppressed persons (e.g. AIDS; organ transplant)

Rate of PCNSL seems to be on the rise, irrespective of immune suppression

Treated with biopsy and chemotherapy

Treatments

Dexamethasone

Adjunctive treatments

• Chemotherapy
• Radiotherapy

GBM - therapy

• Maximal tolerated surgical resection
• Histopathological/molecular dx
• Postoperative scan
• External beam radiotherapy
• 50-60Gy external beam RT
• Role of chemotherapy
  
  • Historically at recurrence
  • Concurrent chemoradiation with temozolomide is new standard of care
  
  

Role of the Neurosurgeon

relief of mass effect

tissue

degree of resection- controversial

awake surgery, mapping, intra-operative imaging, intracavitary therapy

Aids to resection

Functional MRI

Surgical navigation systems

Open MRI

Awake craniotomy