CNS Pathology

Question 1

What is hydrocephalus

Answer 1

Increased volume of CSF within the skull, accompanied by dilatation of the ventricles

In majority of cases of hydrocephalus, there is increased intracranial pressure
Internal hydrocephalus: hydrocephalus involving ventricular dilatation
External hydrocephalus: localised collection of CSF in the subarachnoid space

Question 2

CSF is mainly produced by what structure

Answer 2

The choroid plexus

Question 3

What is the total volume of CSF

Answer 3

120-150 ml

Question 4

What is the flow path for CSF

Answer 4

CSF formed in the lateral ventricles flows through the foramina of Munro to the third ventricle and from there by the aqueduct of Sylvius to the fourth ventricle.
•The fluid then passes through the foramina of Magendie and Luschka of the fourth ventricle to reach the subarachnoid space of the brain. It then spreads through the subarachnoid space over the surface of the spinal cord.
•It is absorbed into the blood by the arachnoid villi present along the

Question 5

What is primary hydrocephalus

Answer 5

Actual increase in the volume of CSF within the skull along with elevated intracranial pressure.
Mechanisms:
•Obstruction to the flow of CSF (commonest).
•Overproduction of CSF.
•Deficient reabsorption of CSF.

Question 6

What is non-communicating hydrocephalus

Answer 6

Occurs when the site of obstruction of CSF pathway is in the third ventricle or at the exit foramina in the fourth ventricle, the ventricular system enlarges and CSF cannot pass into the subarachnoid space

Question 7

What are some common causes of non-communicating hydrocephalus

Answer 7

Congenital non-communicating hydrocephalus e.g. stenosis of the aqueduct, Arnold-Chiari malformation, progressive gliosis of the aqueduct and intra-uterine meningitis.
Acquired non-communicating hydrocephalus may occur from expanding lesion within the skull. These conditions are as under:
•Tumours adjacent to the ventricular system e.g. ependymoma, choroid plexus papilloma, medulloblastoma and others

Question 8

What is communicating hydrocephalus

Answer 8

Occurs when obstruction to the flow of CSF is in the subarachnoid space at the base of the brain, it results in enlargement of the ventricular system but CSF flows freely between dilated ventricles and the spinal canal

Question 9

What are some non-obstructive causes of hydrocephalus

Answer 9

Overproduction of CSF e.g. choroid plexus papilloma
Deficient reabsorption of CSF e.g. following meningitis, subarachnoid haemorrhage and dural sinus thrombosis

Question 10

What is a secondary hydrocephalus

Answer 10

Secondary hydrocephalus is much less common and is defined as compensatory increase of CSF due to loss of neural tissue without associated rise in intracranial pressure (normal pressure hydrocephalus) e.g. from cerebral atrophy and infarction

Question 11

What are some morphological features of hydrocephalus

Answer 11

Grossly, there is dilatation of the ventricles depending upon the site of obstruction. There is thinning and stretching of the brain. The scalp veins overlying the enlarged head are engorged and the fontanelle remain open
•Histologically, severe hydrocephalus may be associated with damage to ependymal lining of the ventricles and cause periventricular interstitial oedema

Question 12

What are some infections of the CNS

Answer 12

Meningitis (acute pyogenic, acute lymphocytic, chronic)
Encephalitis
Brain abscess
Tuberculoma
Neurosyphilis
HIV encephalopathy (AIDS-dementia complex)
Spongiform Encephalopathy (Creutzfeldt-Jakob Disease)
Progressive Multifocal Leucoencephalopathy
Fungal and Protozoal Encephalitis

Question 13

Where are brain abscesses most common

Answer 13

Cerebral hemispheres and less frequent in the cerebellum and basal ganglia

Question 14

Describe a brain abscess

Answer 14

Grossly, it appears as a localised area of inflammatory necrosis and oedema surrounded by fibrous capsule.
Microscopically, the changes consist of liquefactive necrosis in the centre of the abscess containing pus.
It is surrounded by acute and chronic inflammatory cells, neovascularisation, oedema, septic thrombosis of vessels, fibrous encapsulation and zone of gliosis. The CSF and overlying meninges also show evidence of acute and chronic inflammation

Question 15

What is a tuberculoma

Answer 15

An intracranial mass occurring secondary to dissemination of tuberculosis elsewhere in the body. Tuberculomas may be solitary or multiple.
•Grossly, it has a central area of caseation necrosis surrounded by fibrous capsule.
•Microscopically, there is typical tuberculous granulomatous reaction around the central caseation necrosis. A zone of gliosis generally surrounds the tuberculoma. Advanced cases may show areas of calcification

Question 16

What is neurosyphilis

Answer 16

Syphilitic lesions of the CNS used to be common and serious, but more recently there is evidence of atypical neurosyphilis in cases of HIV/AIDS.
•The lesions in syphilis may be in the form of syphilitic meningitis (distinctive perivascular inflammatory reaction of plasma cells and endarteritis obliterans) found in secondary syphilis, and neurosyphilis consisting of tabes dorsalis (slowly progressive degeneration of the posterior roots of the spinal nerves and the posterior columns of the spinal cord by the spirochaetes, what happens to the pupils?) and generalised paralysis of the insane occurring in tertiary stage

Question 17

What is HIV encephalopathy

Answer 17

HIV does not have neurotropism.
•HIV infects the cells of monocyte-macrophage cell line including microglial cells.
•HIV infection then sets in a cascade of toxic mediators and cytokines—TNF-a, IL-1, IL-6, TGF-b, IFN-g, platelet activating factor (PAF) and endothelin, all of which cause damage to the neuroglial tissues.
•Late in the course of AIDS, a group of signs and symptoms of CNS disease appear termed HIV encephalopathy or AIDS-dementia complex. One major clinical feature of this entity is the occurrence of dementia.
•Clinically, the disease develops in about 25% cases of AIDS while autopsy studies reveal presence of HIV encephalopathy in 80-90%

Question 18

What is progressive multifocal leucoencephalopathy

Answer 18

Progressive multifocal leucoencephalopathy (PML) is a slow viral infection of the CNS caused by a papovavirus called JC virus
•PML develops in immunocompromised individual like CMV and Toxoplasma encephalitis does, and is, therefore, an important form of encephalitis due to increasing number of cases of AIDS.
•PML infects oligodendrocytes and causes progressive demyelination at multifocal areas scattered throughout the CNS.
•Grossly, the lesions consist of focal, irregular gelatinous areas most prominent at the junction of grey and white matter. Main areas affected are cerebrum, brainstem, cerebellum, and sometimes spinal cord

Question 19

What are some examples of CVAs

Answer 19

Ischaemic brain damage:
○Generalised reduction in blood flow resulting in global hypoxic-ischaemic encephalopathy
○b) Local vascular obstruction causing infarcts.
● Intracranial spontaneous (non-traumatic) haemorrhage:
○`a) Haemorrhage in the brain parenchyma (intracerebral haemorrhage)
○b) Haemorrhage in the subarachnoid space (subarachnoid haemorrhage).
● Traumatic brain haemorrhage:
○a) Epidural haematoma
○b) Subdural haematoma
○c) Parenchymal brain damage.

Question 20

What is ischemic brain damage

Answer 20

Ischaemic necrosis in the brain results from ischaemia caused by considerable reduction or complete interruption of blood supply to neural tissue which is insufficient to meet its metabolic needs.
The brain requires sufficient quantities of oxygen and glucose so as to sustain its aerobic metabolism, mainly by citric acid (Krebs’) cycle which requires oxygen.
Moreover, neural tissue has limited stores of energy reserves so that cessation of continuous supply of oxygen and glucose for more than 3-4 minutes results in permanent damage to neurons and neuroglial cells

Deprivation of oxygen (anoxia) to the brain may occur in 4 different ways:
●i. Anoxic anoxia, in which there is low inspired pO2.
●ii. Anaemic anoxia, in which the oxygen-carrying haemo - globin is reduced.
●iii. Histotoxic anoxia, in which there is direct toxic injury as occurs in cyanide poisoning.
● iv. Stagnant (ischaemia) anoxia, in which the damage is caused by cessation of blood with resultant local accumulation of metabolites and changes in pH.

In all these different forms of anoxia, the end-result is ischaemic brain damage which may have one of the following two patterns:
●Global hypoxic-ischaemic encephalopathy, resulting from generalised cerebral hypoperfusion.
●Cerebral infarction, resulting from severe localised reduction or cessation of blood supply.

Question 21

What is global hypoxic-ischemic encephalopathy

Answer 21

The brain receives 20% of cardiac output for maintaining its vital aerobic metabolism. A number of factors determine the maximum length of time the CNS can survive irreversible ischaemic damage:
●Severity of the hypoxic episode.
●Presence of pre-existing cerebrovascular disease.
●Age of the patient.
●Body temperature.

In normal individuals, the brain continues to be perfused adequately up to systolic arterial pressure of 50 mmHg by an auto-regulatory vascular control mechanism.
Below this critical value there is risk of ischaemic/hypoxic encephalopathy.
Occurs in cardiac arrest followed by relatively delayed resuscitation, severe episode of hypotension, carbon monoxide intoxication and status epilepticus.
Hypoxic encephalopathy may be followed by either a post-ischaemic confusional state and complete recovery, or a state of coma and even a persistent vegetative life and brain death.

Three types of lesion may occur:
Selective neuronal damage: Neurons are most vulnerable to damaging effect of ischaemia-hypoxia and irreversible injury followed by oligodendrocytes, astrocytes the microglial and vascular endothelium. This is influenced by:
●Different cerebral blood flow
●Presence of acidic excitatory neurotransmitters called excitotoxins.
●Excessive metabolic requirement of these neurons.
●Increased sensitivity of neurons to lactic acid.

Laminar necrosis: In this, superficial areas of cortical layers escape damage while deeper layers are necrosed.
Watershed infarcts: perfusion of overlapping zones, being farthest from the blood supply, suffers maximum damage. Particularly between the anterior and middle cerebral arteries, producing parasagittal infarction.

Question 22

What are the morphological features of a GHIE

Answer 22

The pathologic appearance of the brain in hypoxic encephalopathy varies depending upon the duration and severity of hypoxic episode and the length of survival.
Survival for a few hours: No pathologic changes
Survival 12-24 hours: red neurons.
After 2-7 days: Grossly, there is focal softening. Laminar necrosis and watershed infarcts develop.
Microscopically: reactive fibrillary gliosis, cortical loss of pyramidal cell layer is more severe than that of granular cell layer producing laminar necrosis.

Question 23

What is cerebral infarction

Answer 23

Cerebral infarction is a localised area of tissue necrosis caused by local vascular occlusion—arterial or venous.
Occasionally, it may be the result of non-occlusive causes such as compression on the cerebral arteries from outside and from hypoxic encephalopathy.
Clinically, the signs and symptoms associated with cerebral infarction depend upon the region infarcted. In general, the focal neurologic deficit termed stroke, is present.
However, significant atherosclerotic cerebrovascular disease may produce transient ischaemic attacks (TIA)

Arterial occlusion: Occlusion of the cerebral arteries by either thrombi or emboli is the most common cause of cerebral infarction. Thrombotic occlusion, most frequently, the result of atherosclerosis, and rarely, from arteritis. Embolic occlusion is commonly from from cardiac mural thrombosis.
Venous occlusion: Rare but can occur with increased predisposition to thrombosis. Superior sagittal thrombosis may occur.
Non-obstructive causes: Compression of the cerebral arteries

Grossly, cerebral infarcts may be anaemic or haemorrhagic.
An anaemic infarct: seen after 6-12 hours. Soft and swollen with blurring of junction between grey and white matter.
2-3 days: softening and disintegration.
Eventually, there is central liquefaction with peripheral firm glial reaction and thickened leptomeninges, forming a cystic infarct
A haemorrhagic infarct is red and superficially resembles a haematoma. It is usually the result of fragmentation of occlusive arterial emboli or venous thrombosis.

Question 24

What is the histological outlook of a cerebral infarction

Answer 24

Initially, there is eosinophilic neuronal necrosis and lipid vacuolisation and infiltration by neutrophils.
●2-3 days: there is progressive invasion by macrophages and there is astrocytic and vascular proliferation.
●In the following weeks to months, the macrophages clear away the necrotic debris by phagocytosis followed by reactive astrocytosis, often with little fine fibrosis. haemorrhagic infarcts have haemosiderin leydin macrophages

Question 25

What is a non-traumatic intracranial hemorrhage

Answer 25

Haemorrhage into the brain may be traumatic or nontraumatic, (or spontaneous). There are two main types of spontaneous intracranial haemorrhage:
Intracerebral haemorrhage, which is usually of hypertensive origin.
Subarachnoid haemorrhage, which is commonly aneurysmal in origin.
Other causes of spontaneous intracranial haemorrhage include haemorrhage into tumours, vascular malformations and haemorrhagic diathesis which produce mixed intracerebral and subarachnoid haemorrhage

Question 26

What is an intracerebral hemorrhage

Answer 26

Spontaneous intracerebral haemorrhage occurs mostly in patients of hypertension. Most hypertensives over middle age have microaneurysms in very small cerebral arteries in the brain tissue which can rupture.
The common sites of hypertensive intracerebral haemorrhage are the region of the basal ganglia (particularly the putamen and the internal capsule), pons and the cerebellar cortex.
Clinically the onset is usually sudden with headache and loss of consciousness. Depending upon the location of the lesion, hemispheric, brainstem or cerebellar signs will be present

Question 27

What are the morphological features of an intracerebral hemorrhage

Answer 27

Grossly and microscopically, the haemorrhage consists of dark mass of clotted blood replacing brain parenchyma.
The borders of the lesion are sharply-defined and have a narrow rim of partially necrotic parenchyma.
Small ring haemorrhages in the Virchow-Robin space in the border zone are commonly present.
Ipsilateral ventricles are distorted and compressed and may contain blood in their lumina.
Rarely, blood may rupture through the surface of the brain into the subarachnoid space.
After a few weeks to months, the haematoma undergoes resolution with formation of a slit-like space called apoplectic cyst which contains yellowish fluid.
Its margins are yellow-brown and have haemosiderin-laden macrophages and a reactive zone of fibrillary astrocytosis.

Question 28

What is a subarachnoid hemorrhage

Answer 28

Haemorrhage into the subarachnoid space is most commonly caused by rupture of an aneurysm, and rarely, rupture of a vascular malformation.
Berry aneurysms:
● form at the bifurcation of intracranial arteries and vary in size from 2 mm to 2 cm or more.
●They account for 95% of aneurysms which are liable to rupture. They are not congenital anomalies but develop from defect of the media of the arterial wall at the bifurcation of arteries.
●Increased incidence in association with congenital polycystic kidney disease and coarctation of the aorta.
●About a quarter of berry aneurysms are multiple.

Also occur due to rupture in the posterior circulation, vascular malformations and rupture of mycotic aneurysms that occurs in the setting of bacterial endocarditis.
In all types of aneurysms, the rupture of thin-walled dilatation occurs in association with sudden rise in intravascular pressure but chronic hypertension does not appear to be a risk factor in their development or rupture.
Clinically, berry aneurysms remain asymptomatic prior to rupture. On rupture, they produce severe generalised headache of sudden onset which is frequently followed by unconsciousness and neurologic defects. Initial mortality from first rupture is about 20-25%. Survivors recover completely but frequently suffer from recurrent episodes of fresh bleeding.

Question 29

What are the morphological features of a subarachnoid hemorrhage

Answer 29

Rupture of a berry aneurysm frequently spreads haemorrhage throughout the subarachnoid space with rise in intracranial pressure and characteristic blood-stained CSF.
An intracerebral haematoma may develop if the blood tracks into the brain parenchyma. The region of the brain supplied by the affected artery frequently shows infarction, partly attributed to vasospasm

Question 30

What is a trauma to the CNS

Answer 30

Trauma to the brain constitutes an important cause of death and permanent disability in the modern world.
Important causes of head injuries are: motor vehicle accidents, accidental falls and violence.
Traumatic injuries to the CNS may result in three consequences which may occur in isolation or in combination: 1. Epidural haematoma 2. Subdural haematoma 3. Parenchymal brain damage

Question 31

What is an epidural hematoma

Answer 31

Epidural haematoma is accumulation of blood between the dura and the skull following fracture of the skull, most commonly from rupture of middle meningeal artery. The haematoma expands rapidly since accumulating blood is arterial in origin and causes compression of the dura and flattening of underlying gyri. The patient develops progressive loss of consciousness if haematoma is not drained early

Question 32

What is a subdural hematoma

Answer 32

Subdural haematoma is accumulation of blood between the dura and subarachnoid and develops most often from rupture of veins which cross the surface convexities of the cerebral hemispheres. Subdural haematoma may be acute or chronic.
Acute subdural haematoma develops following trauma and consists of clotted blood, often in the frontoparietal region. There is no significant compression of gyri. Since the accumulated blood is of venous origin, symptoms appear slowly and may become chronic with passage of time if not fatal.
Chronic subdural haematoma occurs often with brain atrophy and less commonly following trauma. Chronic subdural haematoma is composed of liquid blood. Separating the haematoma from underlying brain is a membrane composed of granulation tissue.

Question 33

What is a parenchymal brain damage

Answer 33

Trauma to the CNS may result in damage to brain parenchyma and includes the following forms:
Concussion: caused by closed head injury and is characterised by transient neurologic dysfunction and loss of consciousness. Invariably, there is complete neurologic recovery after some hours to days.
No significant morphologic change is noticed but more severe concussion may cause diffuse axonal injury

Diffuse axonal injury: the most common cause of persistent coma or vegetative state following head injury. The underlying cause is sudden angular acceleration or deceleration resulting in widespread axonal shearing in the deep white matter of both the hemispheres.
Grossly, the changes are minimal to small multiple haemorrhages
Contusions and lacerations: the result of direct (usually blunt) damage to the brain parenchyma, particularly cerebral hemispheres, as occurs in the soft tissues. The overlying skull may or may not be fractured. Traumatic subarachnoid haemorrhage invariably accompanies cerebral contusions.
Microscopically, brain parenchyma at the affected site is haemorrhagic, necrotic and fragmented. On healing, these lesions appear as shrunken areas with golden brown haemosiderin pigment on the surface.
Brain swelling Head injury may be accompanied by localised or diffuse brain swelling.

Question 34

What are demyelinating diseases

Answer 34

A group of neurological disorders with focal or patchy destruction of myelin sheaths in the CNS accompanied by an inflammatory response.
Demyelination may affect peripheral nervous system as well.
Some degree of axonal damage may also occur but demyelination is the predominant feature.
The exact cause for demyelination is not known but currently viral infection and autoimmunity are implicated in its pathogenesis.

Leucodystrophies, slow virus diseases of oligodendrocytes (progressive multifocal leucoencephalopathy), and exposure to toxins (central pontine myelinolysis) all cause demyelination but without associated inflammation and are therefore not considered to be demyelinating diseases.
Only those conditions in which the myelin sheath or the myelin-forming cells (i.e. oligodendrocytes and Schwann cells) are primarily injured and are associated with considerable inflammatory exudate are included under the term ‘demyelinating diseases’.

Question 35

What is multiple (disseminated) sclerosis

Answer 35

●Multiple or disseminated sclerosis is the most common of the CNS demyelinating diseases.
●The usual age at onset is 20 to 40 years.
●Presents as recurrent attacks of focal neurologic disorder with predilection for involvement of the spinal cord, optic nerve and brain.
●The first attack usually begins with a single sign or symptom, most commonly optic neuritis, followed by recovery.
●As the disease becomes more progressive, remissions become infrequent and incomplete.
●The etiology of multiple sclerosis remains unknown but a role for genetic susceptibility, infectious agent and immunologic mechanism has been proposed.

Question 36

What is perivenous encephalomyelitis

Answer 36

Perivenous encephalomyelitis includes two uncommon diseases: acute disseminated encephalomyelitis and acute necrotising haemorrhagic leucoencephalitis.
●Both are monophasic diseases characterised by perivenous mononuclear inflammatory cell infiltration.
●Both diseases occur following a viral infection, vaccination or a respiratory illness.
●Both these conditions are looked upon as human counterpart of experimental allergic encephalomyelitis (EAE) and are considered to be allergic reaction against myelin antigen

Question 37

What is acute disseminated encephalomyelitis

Answer 37

Acute disseminated encephalomyelitis occurs usually following viral infection (measles, mumps, rubella, chickenpox), whooping cough or vaccination.
●The disease begins abruptly with headache and delirium followed by lethargy and coma.
●Signs of meningeal irritation and fever may be present.
●Prognosis for recovery is generally good.

Question 38

What is acute necrotising haemorrhagic leucoencephalitis

Answer 38

Acute necrotising haemorrhagic leucoencephalitis is a rare disease occurring more often after a respiratory infection.
●The clinical course is similar to that of acute disseminated encephalomyelitis except for its suddenness of onset and rapidity of progression, sometimes leading to death within 48 hours.

Question 39

What are degenerative diseases

Answer 39

Degenerative diseases are disorders of unknown etiology and pathogenesis, characterised pathologically by progressive loss of CNS neurons and their processes accompanied by fibrillary astrocytosis.
●The identification of these diseases depends upon exclusion of diseases with known etiologies such as metabolic disturbances, vascular diseases, nutritional deficiencies or infection.
●A considerable proportion of degenerative disorders are genetic in origin, with either dominant or recessive inheritance; others occur sporadically.
●Family history is, of course, of great importance.

●The degenerative disorders usually begin insidiously and have a gradual progressive course over many years.
●In virtually all cases, the lesions have characteristic bilaterally symmetric distribution.
●Particular anatomic or physiologic system of neurons may be selectively affected, leaving others entirely intact.

Question 40

What is Alzheimer’s disease (AD)

Answer 40

Alzheimer’s disease is the most common cause of dementia in the elderly.
●The condition occurs after 5th decade of life and its incidence progressively increases with advancing age.
●The exact cause is not known but a few factors are implicated in its etiology which includes positive family history and deposition of Ab amyloid derived from amyloid precursor protein (APP) forming neuritic ‘senile’ plaques and neurofibrillary tangles.

Grossly, the brain is often reduced in weight and bilaterally atrophic.
●Microscopically, the main features are as under:
○Senile neuritic plaque
○Neurofibrillary tangle
○Amyloid angiopathy
○Granulovacuolar degeneration with dark granules called Hirano bodies

Question 41

What is Parkinsonism

Answer 41

●Parkinsonism is a syndrome of chronic progressive disorder of motor function and is clinically characterised by tremors which are most conspicuous at rest and worsen with emotional stress; other features are rigidity and disordered gait and posture.
●Parkinsonism is caused by several degenerative diseases, the most important being Parkinson’s disease; other causes of parkinsonism are trauma, toxic agents, and drugs (dopamine antagonists).
Grossly, the brain is atrophic or may be normal externally.
●Microscopically, the hallmark is depigmentation of substantia nigra and locus ceruleus due to loss of neuromelanin pigment from neurons and accumulation of neuromelanin pigment in the glial cells.
●Some of the residual neurons in these areas contain intracytoplasmic, eosinophilic, elongated inclusions called Lewy bodies.

Question 42

What are metabolic diseases of the CNS

Answer 42

Metabolic diseases of the CNS result from neurochemical disturbances which are either inherited or acquired.
●Hereditary metabolic disorders predominantly manifest in infancy or childhood and include genetically-determined disorders of carbohydrate, lipid, amino acid and mineral metabolism.
●Acquired or secondary metabolic diseases are the disturbances of cerebral function due to disease in some other organ system such as the heart and circulation, lungs and respiratory function, kidneys, liver, endocrine glands and pancreas.
●In addition, endogenous metabolic diseases may be caused by toxic injuries induced by metals, gases, chemicals, and drugs

Question 43

What are hereditary metabolic diseases of the CNS

Answer 43

Neuronal storage diseases: Storage of a metabolic product in the neurons due to specific enzyme deficiency. Gangliosidoses (Tay-Sachs disease, GM2 gangliosidosis), mucopolysaccharidoses (Gaucher’s disease, Niemann-Pick disease).
●Leucodystrophies: These are diseases of white matter characterised by diffuse demyelination and gliosis. They are caused by deficiency of one of the enzymes required for formation and maintenance of myelin. Sudanophilic leucodystrophy, adrenoleucodystrophy, metachromatic leucodystrophy and globoid cell leucodystrophy (Krabbe’s disease).
●Other inborn errors of metabolism e.g. Wilson’s disease (hepatolenticular degeneration), glycogen-storage diseases, phenylketonuria and galactosaemia.

Question 44

Mention some acquired metabolic diseases

Answer 44

Anoxic-ischaemic encephalopathy
●Hypoglycaemic encephalopathy
●Hyperglycaemic coma
●Acute hepatic encephalopathy (Reye’s syndrome)
●Chronic hepatic encephalopathy
●Kernicterus
●Uraemic encephalopathy
●Encephalopathy due to electrolyte and endocrine disturbances.

Question 45

Mention some nutritional diseases

Answer 45

●Wernicke’s encephalopathy and Korsakoff’s psychosis (vitamin B1 or thiamine deficiency).
●Subacute combined degeneration of the spinal cord (vitamin B12 deficiency).
●Folic acid deficiency
●Spinocerebellar syndrome (vitamin E deficiency).
●Pellagra (niacin deficiency)
●Alcoholic cerebellar degeneration.

Question 46

What are some tumors of the CNS

Answer 46

More than onequarter of the CNS tumours are secondary metastases arising in patients undergoing treatment for systemic cancer.
● Primary CNS tumours are the second commonest form of cancer in infants and children under the age of 15 years, exceeded in frequency only by leukaemia.
●Both benign and malignant CNS tumours are capable of producing neurologic impairment depending upon their site.
●Primary CNS tumours or intracranial tumours include: tumours arising from constituent cells of the brain (with the sole exception of microglial cells) and from the supporting tissues.
●Childhood brain tumours arise from more primitive cells (e.g. neuroblastoma, medulloblastoma).

Question 47

What are gliomas

Answer 47

●The term glioma is used for all tumours arising from neuroglia, or more precisely, from neuroectodermal epithelial tissue.
●Gliomas are the most common of the primary CNS tumours and collectively account for 40% of all intracranial tumours.
●They include tumours arising:
○Astrocytes (astrocytomas and glioblastoma multiforme)
○Oligodendrocytes (oligodendroglioma)
○Ependyma (ependymoma)
○Choroid plexus (choroid plexus papilloma).
●Gliomas may be well-differentiated or poorly-differentiated.
●However, gliomas are never truly well-demarcated or encapsulated and thus all grades of gliomas infiltrate the adjacent brain tissue.
●Gliomas are disseminated to other parts of the CNS by CSF but they rarely ever metastasise beyond the CNS

Question 48

What is an astrocytoma (including Glioblastoma Multiforme)

Answer 48

Astrocytomas are the most common type of gliomas.
●In general, they are found in the late middle life with a peak in 6th decade of life.
●They occur predominantly in the cerebral hemispheres, and occasionally in the spinal cord.
●In children and young adults, pilocytic astrocytomas arise in the optic nerves, cerebellum and brainstem.
●Astrocytomas have tendency to progress from low grade to higher grades of anaplasia. Lowgrade astrocytomas evolve slowly over several years whereas higher grades (anaplastic astrocytoma and glioblastoma multiforme) bring about rapid clinical deterioration of the patient

Question 49

What is the most common type of ganglioma

Answer 49

Astrocytoma

Question 50

What is an oligodendroma

Answer 50

Oligodendroglioma is an uncommon glioma of oligodendroglial origin and may develop in isolation or may be mixed with other glial cells.
●The tumour commonly presents in 3rd to 4th decades of life.
●It occurs in the cerebral hemispheres, most commonly in the frontal lobes or within the ventricles.
●The tumour is generally slow-growing.

Question 51

What is an ependymoma

Answer 51

●Ependymoma is not an uncommon tumour, derived from the layer of epithelium that lines the ventricles and the central canal of the spinal cord.
●It occurs chiefly in children and young adults (below 20 years of age).
●Typically, it is encountered in the fourth ventricle (posterior fossa tumour).
●Other locations are the lateral ventricles, the third ventricle, and in the case of adults, the spinal cord in the region of lumbar spine.
●Clinically, by virtue of their frequent location in the floor of the fourth ventricle, ependymomas are associated with obstructive hydrocephalus.

Question 52

What is the choroid plexus papilloma

Answer 52

Tumours derived from choroid plexus epithelium are uncommon intracranial tumours.
●They are found in the distribution of the choroid plexus.
●In children, they occur most frequently in the lateral ventricles, whereas in adults fourth ventricle is the most common site.
●They are invariably benign tumours and rarely ever undergo malignant transformation.

Question 53

What is a medulloblastoma

Answer 53

Medulloblastoma is the most common variety of primitive neuroectodermal tumour.
●It comprises 25% of all childhood brain tumours but a quarter of cases occur in patients over the age of 20 years.
●The most common location is the cerebellum in the region of roof of fourth ventricle, in the midline of cerebellum, in the vermis, and in the cerebellar hemispheres.
●Medulloblastoma is a highly malignant tumour and spreads to local as well as to distant sites. I
●It has a tendency for widespread metastases to extraneural sites such as to lungs, liver, vertebrae and pelvis.

Question 54

What is a hemangioblastoma

Answer 54

Haemangioblastoma is a tumour of uncertain origin and constitutes about 2% of all intracranial tumours.
●It is seen more commonly in young adults and is commoner in males.

Question 55

What is a primary CNS lymphoma

Answer 55

Lymphomas in the brain may occur as a part of disseminated non-Hodgkin’s lymphoma or may be a primary CNS lymphoma.
● The incidence of the primary CNS lymphoma has shown a rising trend in patients of AIDS and other immunosuppressed conditions.
●They occur in persons above 5th decade of life.
●Primary CNS lymphoma has a poor prognosis.

Question 56

What are germ cell tumors

Answer 56

●Rarely, germ cell tumours may occur in the brain, especially in children.
●Common locations are suprasellar region and pineal area.
●Some common examples of such tumours are germinoma (seminoma/dysgerminoma), teratoma and embryonal carcinoma.

Question 57

What is a meningioma

Answer 57

Meningiomas arise from the cap cell layer of the arachnoid.
●Their most common sites are in the front half of the head and include: lateral cerebral convexities, midline along the falx cerebri adjacent to the major venous sinuses parasagittally, and olfactory groove.
●Meningiomas are generally solitary.
●Most meningiomas are benign and can be removed successfully.
●Rarely, a malignant meningioma may metastasise, mainly to the lungs.

Question 58

What are metastatic tumors

Answer 58

Approximately a quarter of intracranial tumours are metastatic tumours.
●Most common primary tumours metastasising to the brain are: carcinomas of the lung, breast, skin (malignant melanoma), kidney and the gastrointestinal tract and choriocarcinoma.
●Infiltration from lymphoma and leukaemias may also occur.