Intra cranial space occupying lesions

Dr Bindu K   BHMS,MD(HOM)
These are lesions which expand in volume to displace normal neural structures & lead to increase in intra – cranial pressure.

PATHOLOGY :–
Symptoms are produced due to,
1. Irritation & destruction of brain tissue causing neurological phenomena,eg. epilepsy, paralysis.

2. Raised intra cranial pressure:- The rate of increase of tension depend on the nature of the lesion and its location. Posterior fossa lesions lead to more rapid rise in tension than supratentorial lesions.

3. False localizing signs :-

• Neurological phenomena arising from the secondary effects of lesion like herniation of neural tissue under the falx-cerebri or downward herniation through tentorium cerebelli or foramen magnum, pressure effects on other parts of brain develop.
• Countre – coup effect:- This is pressure effect caused on the side opposite to the side of lesion when a space occupying lesion expands. The midline structures such as brainstem may be pushed towards the opposite free margin of tentorium cerebelli to give rise to compression of normal side also.
• In addition to this , different lesions may produce symptoms specific to their nature like fever in case of brain abscess, signs of meningeal irritation in subarachnoid haemorrhage

Classification of intra cranial space occupying lesions :-

• I. Congenital :- Dermoid, Epidermoid, Teratoma.
• II. Traumatic :- Subdural & Extradural haematoma
• III. Inflammatory :- Abscess, Tuberculoma, Syphilitic gumma,fungal Granulomas.
• IV. Parasitic :- Cysticercosis, Hydratid cyst, Amebic abscess, Schistosoma japonicum.
• V. Neoplasms 

a) Tumors arising from neural structures: Gliomas – astrocytoma, ependymoma, oligodendroglioma, germinoma, medulloblastoma.
b) Tumors arising from appendages: Meningioma, schwannoma, chondroma, osteoma.
c) Pituitary lesions : Pituitary adenoma, Craniopharyngioma.
d) Vascular lesions : Angioma, Hemangioblastoma, Papilloma of choroid plexus.
e) Secondary neoplasms.

Clinical features :-
1. Persistent headache not due to any other detectable cause and unresponsive to medication. This may be due to focal irritation, displacement of pain sensitive structures or due to increased intra- cranial tension. If due to increased intra- cranial tension headache develop rapidly over several minutes persist for 20-40 minutes and subside quickly. May awaken the patient from sound sleep 60-70 mts after retiring and also precipitated by coughing, sneezing, vomiting etc.
2. Vomiting & visual loss :- projectile vomiting unassociated with nausea.
3. Papilledema in increased intra- cranial tension.
4. Recent onset behaviour changes.
5. Late onset seizures :- Any type of seizure occuring for the first time after the age of 15 years should suggest the possibility of intra cranial space occupying lesions. It is due to disruption of cortical circuits by tumours that invade or compress cerebral cortex.
6. Sudden onset of neurological deficits like dementia, personality changes, gait disorders etc.

Intracranial haematomas
I. Extra dural haematomas :-
Collection of blood between the dura & the skull due to injury to the middle meningeal vein, middle meningeal artery, diploic vein, dural venous sinuses or small vessels lying between dura and skull. Common site is temporal fossa.

Pathogenesis :-
Initial collection of blood in the extradural space causes stripping of the dura from bone. Symptoms are produced when symptoms exceed 25 ml in volume. Extent and location of haematomas are determined by the ease of stripping of the dura, site of injury, its severity, and presence of depressed fractures of the skull.

Clinical features :-
1. 1 – 2% persons suffering from head injury develop extra dural haematoma.
2. Uncommon in children below 3 yrs and in old age – adherance of dura
To the skull prevents its easy stripping.
3. Progressive deterioration of level of consciousness :- there may be a period of immediate loss of consciousness, after that a period of apparent normalcy with clear consciousness followed by deterioration of mental state.
4. Pupillary changes :- called Hutchinson’s pupillary reaction – pupil on the side of lesion constricts initially then it dilates and as intra cranial tension increases the opposite pupil also dilates.

Investigation :-

• CT scan 
• MRI
• Cerebral angiography.

II. Subdural haematomas :-
Collection of blood between the dura and the arachnoid. Usually follow injuries which may be apparently trivial or even unnoticed. Common causes are bleeding from superficial veins or venous sinuses. Anticoagulant treatment predispose to intracranial bleeding and subdural haematoma. Usual sites are frontal, anterior temporal,& parietal.

Pathology :-
Haematoma consists of fluid blood covered on inner and outer aspects by layers of fibrin. Blood is defibrinated due to the constant pulsation of the brain. High protein content of fluid makes it hyperosmotic. So it absorbs fluid from the surrounding and enlarges leading to increase in intra cranial tension.

Clinical features :– Manifestation may be acute or chronic in nature.
Acute : Clinical features are similar to extra dural hematoma.
Chronic : Dementia, altered behaviour, psychiatric manifestations or
focal neurological deficits may develop.
In middle aged headache, contralateral hemiplegia, papilledema and in children vomiting, restlessness. Irritability, refusal to feed, anaemia, seizures and failure to thrive are common presenting symptoms.

Investigation :-
CT scan
MRI
Cerebral angiography.

Neoplasms of brain
About 50 % of intracranial tumors are primary neoplasms and the rest secondary. Out of this 50 – 60 % of primary brain tumors are gliomas, 25% – meningiomas, 10% – schwannoma and the remainder others.

Etiology:
1. Exposure to ionizing radiations is the only well documented enviornmental risk factor.
2. A number of heriditary factors are associated with an increased risk of brain tumours, eg. Neurofibromatosis type – I and type – II, Multiple endocrine neoplasia type –I.
3. Genes also contribute to the development of brain tumours and other malignancies. There are two classes of genes namely, tumour suppressor genes and proto oncogenes. There is over – expression of proto oncogenes in brain tumours.
Clinical course of brain tumours :-

There are four stages of development of tumour.

• Stage I : Initial period of silent growth.
• Stage II : Stage of focal syndromes like epilepsy.
• Stage III : Increased intracranial tension.
• Stage IV : Brain displacement and false localizing signs.

Primary neoplasmas of brain :
I. Astrocytomas :
Derived from astrocytes. Common sites are cerebrum, cerebellum, thalamus, pons and optic chiasma. Slow growing tumour. Most commonly used grading system is WHO four tired grading system.

WHO grading,

• Grade I – Least malignant with excellent prognosis after surgical excision, eg. pilocytic astrocytoma.
• Grade II – Astroblastoma
• Grade III – Anaplastic astrocytoma
• Grade IV – Glioblastoma multiforme – clinically aggressive

Astrocytomas occur in three forms namely, diffuse or infiltrating, solid and cystic.

Prognosis :-
Poor prognosis in age over 65 years, poor functional status in grade III and grade IV astrocytomas.
Low grade astrocytoma :- usually in children, spindle shaped cell (pilocytic astrocytoma), occurs from cerebellum, well demarcated, cystic. Complete surgical excision usually produces long term survival.
High grade astrocytoma :- seen in adults, usually supra – tentorial, no clearly defined margins, infiltration to white matter and metastasis to spine through CSF called drop metastasis occurs. Usually fatal and total surgical excision is not possible.
Gliomatosis cerebri :-Rare form with diffuse infiltration of the brain by malignant astrocytes without a focal enhancing mass.
Treatment :-whole brain radiation therapy in selected patients with chemotherapy.

II. Oligodendrogliomas :-
Slow growing tumour compared to astrocytoma. They contain mixture of cells with astrocytic and oligodendroglial features called mixed glioma. Usually supratentorial. 50% of patients with 5 year survival.
25– 34% with 10 year survival. Less infiltrative and complete surgical excision possible.

III. Ependymoma :-
Arise from spinal cord especially from lumbo-sacral region in adults and from ventricles especially fourthventricle in children.
Histologically myxopapillary that is, papillary arrangement of cells and mucin production. Usually relatively demarcated from adjucent neural tissue. Metastasis through CSF occurs.
Gross total excision provides 5 year disease free survival in 80% cases.

IV. Germinoma :-
A variety of germ cell tumor arising in midline structures.Common site within or adjacent to 3rd ventricle. Due to their location causes features of hypothalamic dysfunction like diabetes incipedus, visual field defects, disturbances of memory and hydrocephalus.
Radiosensitive and chemosensitive. 5 year survival in 80% patients.

V. Medulloblastoma :-
Arise from neural precurssor cells. The most frequent malignancy of children. Rapidly growing tumours affecting vermis of the cerebellum and giving rise to wide spread metastasis.

VI. Meningioma :-
Arise from arachnoid cells particularly seen in sites having arachnoid granulations. Those are usually benign and attached to dura. More common in women. Invades skull rarely invades brain.
Common sites are along sagital sinus, c-p angle and along the dorsum of spinal cord.
Treatment : Surgical resection and post – operartive radiation.

VII. Schwannoma :-
Arise from Schwann cells of nerve roots. Commonly from 8th cranial nerve and less commonly 5th cranial nerve is affected. It can arise from any cranial nerve except optic and olfactory (myelinated by oligodendroglia). Neurofibromatosis type – II predisposes to vestibular schwannoma. Neurofibromatosis type – I predisposes to schwannoma of spinal nerve roots.
Clinical features are progressive unilateral hearing loss, tinitis, vertigo.
Treatment : Surgical excision.

VIII. Craniopharyngioma :-
Arise from remnants of the pituitary stalk called Rathke’s pouch
(mesodermal structures from which anterior pituitary gland is derived). Cystic supracellar tumour and in adults usually calcified.
Clinical features are growth failure in children, endocrinal disturbances due to pressure on hypothalamus like diabetes incipedus, somnolence, obesity, hyperphagia and visual loss.

Metastatic tumors of brain :-
Common route is through haematogenous.Primary site is lung in most of the cases. Usually from carcinoma breast metastasis occurs to cerebellum and posterior pituitary gland. Others are GIT malignancies, melanoma, thyroid cancer, Hodgkin’s lymphoma. In brain the usual site of metastasis is the grey matter – white matter junction and border zone between middle cerebral and posterior cerebral artery distribution. Usually incurable. Palliative therapy and radiotherapy are the treatment of choice.

Investigations :-
In primary brain tumour no increase in ESR and tumor specific antigen.
In metastatic tumours associated with systemic signs of malignancy.
Lumbar puncture – Should not be performed in patients with mass lesion it may precipitatebrain herniation.
CSF : increase opening pressure, elevated protein level, mild lymphocytic pleocytosis and rarely contains malignant cells.
EEG : to distinguish epileptic seizures produced by focal lesions and idiopathic epilepsy.
CT Scan, MRI, PET, SPECT