Brain

Question 1

Encephalocele

Answer 1

refers to an extrusion of malformed brain tissue through a midline defect in the cranium. It most often occurs in the occiput, although nasofrontal variants involving the orbit, ethmoid, or cribriform plate

Associations
Chiari malformations
Dandy-Walker malformations
Meckel-Gruber syndrome

Question 2

Spinal dysraphism or spina bifida

Answer 2

(the most common neural tube defects) may be an asymptomatic bony defect (spina bifida occulta) or a severe malformation with a flattened, disorganized segment of spinal cord, associated with an overlying meningeal outpouching.

Question 3

Lissencephaly

Answer 3

Lissencephaly is a malformation characterized by reduction in the number of gyri, which in the extreme case may show no gyral pattern (agyria)

Question 4

Polymicrogyria

Answer 4

Polymicrogyria is characterized by numerous small, irregularly formed cerebral convolutions with shallow sulci. The cerebral cortex is composed of four or fewer layers (instead of the normal six layers), with fusion of the molecular layers between gyri. Polymicrogyria can be induced by localized tissue injury toward the end of neuronal migration, although genetically determined forms, which are typically bilateral and symmetric, are also recognized.

Question 5

Neuronal heterotopias

Answer 5

Neuronal heterotopias are a group of migrational disorders defined by collections of subcortical neurons in inappropriate locations along the pathway of migration. As might be expected, one location is along the ventricular surface—as though the cells never left their place of birth. Periventricular nodular heterotopias can be caused by mutations in the gene encoding filamin A.

Question 6

Holoprosencephaly

Answer 6

Holoprosencephaly is a spectrum of malformations c acterized by incomplete separation of the cerebral hemispheres across the midline. Severe forms manifest midline facial abnormalities, including cyclopia; less severe variants (arrhinencephaly) show absence of the olfactory cranial nerves and related structures.

Holoprosencephaly is associated with trisomy 13 as well as other genetic syndromes. Mutations in genes that encode components of the sonic hedgehog signaling pathway may also produce holoprosencephaly.

Question 7

Diffuse Axonal Injury

Answer 7

Traumatic brain injuries may also damage the deep white matter regions, cerebral peduncles, superior colliculi, and deep reticular formation in the brainstem.

The microscopic findings include axonal swelling, indicative of diffuse axonal injury, and focal hemorrhagic lesions. As many as 50% of individuals who develop coma shortly after trauma, even without cerebral contusions, are believed to have diffuse axonal injury.

Question 8

Although the brain accounts for only x% of body weight, it receives approximately x% of the resting cardiac output and accounts for x% of the body’s oxygen consumption.

Answer 8

Although the brain accounts for only 1% to 2% of body weight, it receives approximately 15% of the resting cardiac output and accounts for 20% of the body’s oxygen consumption.

Question 9

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominant disorder caused by mutations in the x gene that lead to misfolding of the extracellular domain of the x receptor.

Answer 9

NOTCH3
NOTCH3 receptor.

The disease is characterized clinically by recurrent small vessel strokes (usually infarcts, less often hemorrhages) and dementia. Imaging studies show that the first detectable changes are in white matter, usually presenting around 35 years of age and then progressing further over time.

Question 10

Saccular aneurysms are found in about x% of the population according to recent data from community-based radiologic studies.

About x% of saccular aneurysms are found near major arterial branch points in the anterior circulation; multiple aneurysms exist in x% of cases based on autopsy series.

Answer 10

Saccular aneurysms are found in about 2% of the population according to recent data from community-based radiologic studies.

About 90% of saccular aneurysms are found near major arterial branch points in the anterior circulation; multiple aneurysms exist in 20% to 30% of cases based on autopsy series.

Question 11

Saccular aneurysms - increased incidence in individuals with certain Mendelian disorders (x)

Common locations?

Answer 11

increased incidence in individuals with certain Mendelian disorders (e.g., autosomal dominant polycystic kidney disease, Ehlers-Danlos syndrome typeIV, neurofibromatosis type 1 [NF1], and Marfan syndrome), fibromuscular dysplasia of extracranial arteries, and coarctation of the aorta. Other predisposing factors include cigarette smoking and hypertension (estimated to be present in about half of affected individuals).

Question 12

Brain aneurysms greater than xmm in diameter have a roughly x% risk of bleeding per year.

Between x% of patients die with the first rupture

Answer 12

Aneurysms greater than 10 mm in diameter have a roughly 50% risk of bleeding per year.

Between 25% and 50% of patients die with the first rupture

Question 13

Vascular malformations of the brain are classified into four principal groups: …

Answer 13

arteriovenous malformations
cavernous malformations
capillary telangiectasias
venous angiomas.

Question 14

There are four principal routes by which microbes enter the nervous system…

Answer 14

There are four principal routes by which microbes enter the nervous system.

• Hematogenous spread is the most common; infectious agents ordinarily gain access through the arterial circulation, but retrograde venous spread can occur via anastomoses with veins of the face.
• Direct implantation of microorganisms is most often traumatic, but can be sometimes associated with congenital malformations (e.g., meningomyelocele) that provide ready access for microorganisms.
• Local extension can originate from infected adjacent structures, such as air sinuses, teeth, skull, or vertebrae.
• Viruses also may be transported along the peripheral nervous system, as occurs with rabies and herpes zoster viruses.

Question 15

Meningitis is an inflammatory process of the x and x, usually caused by an infection.

Answer 15

Meningitis is an inflammatory process of the leptomeninges and CSF within the subarachnoid space, usually caused by an infection.

Question 16

Common Central Nervous System Infections - bacterial

Answer 16

Question 17

Common Central Nervous System Infections - viral

Answer 17

Question 18

Common Central Nervous System Infections - spirochete, fungal, protozoa

Answer 18

Question 19

Waterhouse-Frederichsen syndrome

Answer 19

meningitis-associated septicemia and hemorrhagic infarction of the adrenal glands

It occurs most often with meningococcal and pneumococcal meningitis. In the immunosuppressed individual, purulent meningitis may be caused by several other infectious agents, such as Klebsiella or anaerobic organisms, and may have an atypical clinical course and uncharacteristic CSF findings, rendering timely diagnosis more difficult.

Question 20

The most common pattern of tuberculous involvement is a diffuse meningoencephalitis. The subarachnoid space contains a gelatinous or fibrinous exudate that characteristically involves the x of the brain, effacing the cisterns and encasing cranial nerves.

Answer 20

base

Question 21

Neurosyphilis presents in several distinct forms.

Answer 21

• Meningovascular neurosyphilis is chronic meningitis involving the base of the brain and more variably the cerebral convexities and spinal leptomeninges. In addition, there may be an associated obliterative endarteritis (Heubner arteritis) accompanied by a distinctive perivascular inflammatory reaction rich in plasma cells and lymphocytes. Cerebral gummas (plasma cell-rich mass lesions) may also occur in the meninges and extend into the parenchyma.
• Paretic neurosyphilis is caused by invasion of the brain by T. pallidum and manifests as insidious but progressive cognitive impairment associated with mood alterations (including delusions of grandeur) that terminate in severe dementia (general paresis of the insane). Parenchymal damage of the cerebral cortex is particularly common in the frontal lobe, but also occurs in other areas of the isocortex. The lesions are characterized by loss of neurons, proliferation of microglia, gliosis, and iron deposits; the latter are demonstrable with the Prussian blue stain perivascularly and in the neuropil, and are presumably the sequelae of small bleeds stemming from microvascular damage. The spirochetes can, at times, be demonstrated in tissue sections.
• Tabes dorsalis is the result of damage to the sensory axons in the dorsal roots. This causes impaired joint position sense and ataxia (locomotor ataxia); loss of pain sensation, leading to skin and joint damage (Charcot joints); other sensory disturbances, particularly the characteristic “lightning pains”; and absence of deep tendon reflexes. On microscopic examination, there is loss of both axons and myelin in the dorsal roots, with corresponding pallor and atrophy in the dorsal columns of the spinal cord. Organisms are not demonstrable in the cord lesions.

Question 22

Herpes simplex virus type 1 (HSV-1) encephalitis occurs most commonly in x.

Answer 22

Herpes simplex virus type 1 (HSV-1) encephalitis occurs most commonly in children and young adults; only about 10% of affected individuals have a history of prior herpetic infection.

Question 23

Herpes simplex virus type 2 (HSV-2) can infect the nervous system.

In x(age group) it causes meningitis, but as many as x% of neonates born by vaginal delivery to women with active primary HSV genital infections acquire the infection during passage through the birth canal and develop severe encephalitis.

In individuals with active HIV infection, HSV-2 may cause x and x encephalitis.

Answer 23

In adults it causes meningitis, but as many as 50% of neonates born by vaginal delivery to women with active primary HSV genital infections acquire the infection during passage through the birth canal and develop severe encephalitis.

In individuals with active HIV infection, HSV-2 may cause an acute hemorrhagic and necrotizing encephalitis.

Question 24

CMV infection of the nervous system occurs in x(age group) and x individuals.

Answer 24

CMV infection of the nervous system occurs in fetuses and immunosuppressed individuals.

The outcome of infection in utero is periventricular necrosis that produces severe brain destruction followed later by microcephaly and periventricular calcification. CMV is a common opportunistic viral pathogen in individuals with AIDS, with CNS involvement also occurring in this setting.

Question 25

The most commonly encountered fungi that invade the brain are x and x. x usually produces multiple x, with or without granuloma formation; in contrast, parenchymal aggregates of x organisms are typically found within expanded x and are associated with minimal to no inflammation or gliosis.

Answer 25

Candida and Cryptococcus.

Candidiasis usually produces multiple microabscesses, with or without granuloma formation; in contrast,

parenchymal aggregates of Cryptococcal organisms are typically found within expanded perivascular (Virchow-Robin) spaces and are associated with minimal to no inflammation or gliosis.

Cryptococcal meningitis, a common opportunistic infection in the setting of AIDS, may be fulminant and fatal in as little as 2 weeks or indolent, evolving over months or years.

Question 26

MS is caused by an autoimmune response directed against components of the x

Answer 26

myelin sheath.

geographic variation in the prevalence of MS, with a higher number of cases diagnosed away from the equator; it has been proposed that this latitude dependence may be related to a low level of vitamin D (an immune system modulator) in people who are not exposed to sunlight during winter.

MS is 15-fold higher when the disease is present in a first-degree relative and roughly 150-fold higher with an affected monozygotic twin.

Question 27

Neuromyelitis optica (NMO) is a syndrome with x

Answer 27

Neuromyelitis optica (NMO) is a syndrome with synchronous (or near-synchronous) bilateral optic neuritis and spinal cord demyelination. Once considered a variant of MS, it is clearly a distinct disorder. NMO has an even greater skewing toward women than MS, is more commonly associated with poor recovery from the first attack, and is often characterized by the presence of aquaporin-4 antibodies, which appear to be pathogenic.

Question 28

The pathologic process that is common across most of the neurodegenerative diseases is x

Answer 28

the accumulation of protein aggregates

Neurodegenerative diseases are disorders characterized by the progressive loss of particular groups of neurons, which often have shared functions.

Question 29

Features of the Major Neurodegenerative Diseases

Answer 29

Question 30

Alzheimers disease

The major microscopic abnormalities of AD are x and x.

Answer 30

Neuritic plaques are focal, spherical collections of dilated, tortuous, axonal or dendritic processes (dystrophic neurites) often around a central amyloid core, which may be surrounded by a clear halo

Neurofibrillary tangles are tau-containing bundles of filaments in the cytoplasm of the neurons that displace or encircle the nucleus. In pyramidal neurons, they often have an elongated “flame” shape; in rounder cells, the basket weave of fibers around the nucleus takes on a rounded contour (“globose” tangles).

Question 31

The fundamental abnormality in AD is the accumulation of two proteins (x and x) in specific brain regions, likely as a result of excessive production and defective removal

Answer 31

Aβ and tau

The two pathologic hallmarks of AD, particularly evident in the end stages of the illness, are amyloid plaques and neurofibrillary tangles.

Question 32

Parkinson Disease is a neurodegenerative disease marked by a hypokinetic movement disorder that is caused by

Answer 32

loss of dopaminergic neurons from the substantia nigra.

Question 33

Atypical parkinsonian syndromes or Parkinson-plus syndromes…

Answer 33

Progressive supranuclear palsy
corticobasal degeneration, both of which are tauopathies,

and multisystem atrophy, a synucleinopathy.

Question 34

HD is an x(inheritance) disease

HD is a prototypic (genetic) disease

The gene for HD, HTT, located on chromosome 4p16.3, encodes a 348-kD protein known as x.

Answer 34

AD

HD is a prototypic polyglutamine trinucleotide repeat expansion disease
In the first exon of the gene, there is a stretch of CAG repeats that encodes a polyglutamine region near the N terminus of the protein. Normal HTT genes contain 6 to 35 copies of the repeat; when the number of repeats is increased beyond this level, it is associated with disease. There is an inverse relationship between repeat number and age of onset, such that longer repeats tend to be associated with earlier onset.

huntington

HD caused by degeneration of striatal neurons and characterized by a progressive movement disorder and dementia.

Question 35

Multiple System Atrophy is a sporadic disorder that affects several functional systems in the brain and is characterized by x in the cytoplasm of oligodendrocytes.

Answer 35

α-synuclein inclusions

Question 36

Features of Diffuse Gliomas

Answer 36

Question 37

Unique histopathologic feature of pilocystic astrocytoma

Answer 37

Distinct genetic alterations of the MAP kinase pathway, the most common being a KIAA1549-BRAF gene fusion/ duplication.

Question 38

Distinct lesions that occur in the filum terminale of the spinal cord

Answer 38

Myxopapillary ependymomas

Question 39

Gangliogliomas are most commonly found in the x lobe and often have a x component.

Answer 39

Gangliogliomas are most commonly found in the temporal lobe and often have a cystic component.

Question 40

Molecular subtypes of medulloblastoma have been identified through genomic studies, revealing alterations of signaling pathways involved in normal cerebellar development, such as the x pathway (which is involved in control of normal proliferation of cerebellar granule cells) and the x pathway.

Answer 40

sonic hedgehog–patched (SHH) pathway (which is involved in control of normal proliferation of cerebellar granule cells)

WNT/β-catenin signaling pathway.

Question 41

Primary CNS lymphoma accounts for x% of extranodal lymphomas and x% of intracranial tumors.

It is the x CNS neoplasm in immunosuppressed individuals, including those with AIDS and immunosuppression after transplantation.

Answer 41

Primary CNS lymphoma accounts for 2% of extranodal lymphomas and 1% of intracranial tumors. It is the most common CNS neoplasm in immunosuppressed individuals, including those with AIDS and immunosuppression after transplantation.

Question 42

Meningioma. Common sites of involvement include the x, x, x, x, x, and x.

Answer 42

Meningioma. Common sites of involvement include the parasagittal aspect of the brain convexity, dura over the lateral convexity, wing of the sphenoid, olfactory groove, sella turcica, and foramen magnum.

Question 43

Metastases to brain. The five most common primary sites are …

Answer 43

lung, breast, skin (melanoma), kidney, and gastrointestinal tract, accounting for about 80% of all metastases combined.

Some rare tumors (e.g., choriocarcinoma) have a high likelihood of metastasizing to the brain, whereas other more common tumors (e.g., prostatic adenocarcinoma) almost never do so.

Question 44

Tuberous sclerosis complex (TSC) is a x(inheritance) syndrome that occurs at a frequency of approximately 1 in 6000 births.

It is characterized by the development of x and benign neoplasms involving the brain and other tissues; the most frequent clinical manifestations are x, x, and x.

Answer 44

Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome that occurs at a frequency of approximately 1 in 6000 births.

It is characterized by the development of hamartomas and benign neoplasms involving the brain and other tissues; the most frequent clinical manifestations are seizures, autism, and intellectual disability.

Question 45

Tuberous sclerosis complex

Hamartomas within the CNS take the form of x and x. x are benign neoplasms that appear to develop from the hamartomatous nodules in the same location.

Elsewhere in the body, renal x, retinal x, pulmonary x, and cardiac x develop during childhood and adolescence.

Answer 45

Hamartomas within the CNS take the form of cortical tubers and subependymal nodules. Subependymal giant cell astrocytomas are benign neoplasms that appear to develop from the hamartomatous nodules in the same location.

Elsewhere in the body, renal angiomyolipomas, retinal glial hamartomas, pulmonary lymphangioleiomyomatosis, and cardiac rhabdomyomas develop during childhood and adolescence.

Cysts may be found at various sites, including the liver, kidneys, and pancreas. Cutaneous lesions include angiofibromas, localized leathery thickenings (shagreen patches), hypopigmented areas (ash-leaf patches), and subungual fibromas.

Question 46

Von Hippel-Lindau Disease

Individuals with this x(inheritance) disease develop x of the CNS; cysts that involve the x, x, and x; x; and x.

x are most common in the x and x, but may also occur in other CNS locations.

Answer 46

Von Hippel-Lindau Disease

Individuals with this autosomal dominant disease develop hemangioblastomas of the CNS; cysts that involve the pancreas, liver, and kidneys; renal cell carcinomas; and pheochromocytomas. Hemangioblastomas are most common in the cerebellum and retina, but may also occur in other CNS locations.

Question 47

Paraneoplastic syndromes that involve the peripheral and/ or central nervous systems and can precede the clinical recognition of the primary tumor.

Ilustrative CNS examples are as follows:

Answer 47

Subacute cerebellar degeneration is associated with d tion of Purkinje cells, gliosis, and a chronic inflammatory cell infiltrate. One group of affected patients has a circulating PCA-1 antibody (anti-Yo) that recognizes cerebellar Purkinje cells; this antibody occurs predominantly in women with ovarian, uterine, or breast carcinomas.

• Limbic encephalitis is characterized by subacute dementia and shows perivascular inflammatory cuffs, microglial nodules, some neuronal loss, and gliosis, all of which are most evident in the anterior and medial portions of the temporal lobe; the microscopic picture resembles that of a viral encephalitis. A comparable process involving the brainstem can be seen in isolation or together with limbic system involvement.

Eye movement disorders, most commonly opsoclonus, may occur by themselves or in association with other evidence of cerebellar and brainstem dysfunction. In children, this is most commonly associated with neuroblastoma and is often accompanied by myoclonus.

The peripheral nervous system can also be affected by the following paraneoplastic syndromes:

• Subacute sensory neuropathy may be found in association with limbic encephalitis or in isolation. It is marked by loss of sensory neurons and lymphocytic inflammation in the dorsal root ganglia.
• Lambert-Eaton myasthenic syndrome is caused by antibodies against the voltage-gated calcium channel in the presynaptic elements of the neuromuscular junction. This syndrome can also be seen in the absence of malignancy.

Question 48

Hormones released by the anterior pituitary.

Answer 48

Question 49

Classification of pituitary adenomas

Answer 49

Question 50

x adenomas are the most common type of hyperfunctioning pituitary adenoma, accounting for about 30% of clinically recognized cases.

x adenomas are the second most common type of functioning pituitary adenoma

x adenomas are uncommon, accounting for approximately 1% of pituitary adenomas.

Answer 50

Prolactin-secreting lactotroph adenomas are the most common type of hyperfunctioning pituitary adenoma, accounting for about 30% of clinically recognized cases.

Growth hormone (GH)-secreting somatotroph adenomas are the second most common type of functioning pituitary adenoma, and cause gigantism in children and acromegaly in adults.

Thyrotroph (TSH-producing) adenomas are uncommon, accounting for approximately 1% of pituitary adenomas. They are a rare cause of hyperthyroidism.

Question 51

Hypofunction of the anterior pituitary occurs when approximately x% of the parenchyma is lost or absent.

x and x are among the most common causes of pituitary hypofunction.

• Pituitary apoplexy:
• Ischemic necrosis of the pituitary (x syndrome)

Answer 51

Hypofunction of the anterior pituitary occurs when approximately 75% of the parenchyma is lost or absent.

• Tumors and other mass lesions: Pituitary adenomas, other benign tumors arising within the sella, primary and metastatic malignancies, and cysts can cause hypopituitarism. Any mass lesion in the sella can cause damage by exerting pressure on adjacent normal pituitary cells.
• Traumatic brain injury and subarachnoid hemorrhage are among the most common causes of pituitary hypofunction.
• Pituitary surgery or radiation: Surgical excision of a pituitary adenoma may inadvertently include the nonadenomatous pituitary. Radiation of the pituitary, used to prevent regrowth of residual tumor after surgery, can damage the nonadenomatous pituitary.
• Pituitary apoplexy: caused by a sudden hemorrhage into the pituitary gland, often occurring into a pituitary adenoma. In its most dramatic presentation, apoplexy causes the abrupt onset of excruciating headache, diplopia due to pressure on the oculomotor nerves, and acute hypopituitarism. In severe cases, it can cause cardiovascular collapse, loss of consciousness, and even sudden death. The combination of mass effect from the hemorrhage and acute hypopituitarism makes pituitary apoplexy a neurosurgical emergency.
• Ischemic necrosis of the pituitary (Sheehan syndrome), also known as postpartum necrosis, is the most common form of ischemic necrosis of the anterior pituitary. During pregnancy, the anterior pituitary enlarges to almost twice its normal size. This physiologic expansion of the gland is not accompanied by an increase in blood supply from the low-pressure venous system; hence, there is relative hypoxia. Any further reduction in blood supply caused by obstetric hemorrhage or shock may precipitate infarction of the anterior lobe. Because the posterior pituitary is supplied directly from arterial branches, it is much less susceptible to ischemic injury and is therefore usually unaffected. Pituitary necrosis may also be encountered in disseminated intravascular coagulation and, less commonly, in sickle cell anemia, elevated intracranial pressure, traumatic injury, and shock of any origin. Whatever the pathogenesis, the ischemic area is resorbed and replaced by a nubbin of fibrous tissue attached to the wall of an empty sella.
• Rathke cleft cyst: These cysts, lined by ciliated cuboidal epithelium with occasional goblet cells and anterior pituitary cells, can accumulate proteinaceous fluid and expand, compromising the normal gland.
• Empty sella syndrome: Any condition or treatment that destroys part or all of the pituitary gland, such as ablation of the pituitary by surgery or radiation, can result in an empty sella and the empty sella syndrome. There are two types: (1) In a primary empty sella, a defect in the diaphragma sella allows the arachnoid mater and cerebrospinal fluid to herniate into the sella, expanding the sella and compressing the pituitary. Classically, this occurs in obese women with a history of multiple pregnancies. Affected individuals often present with visual field defects and occasionally with endocrine anomalies, such as hyperprolactinemia, due to interruption of inhibitory hypothalamic inputs. Sometimes the loss of functioning parenchyma is sufficient to produce hypopituitarism. (2) In secondary empty sella, a mass, such as a pituitary adenoma, enlarges the sella and is then either surgically
  removed or undergoes infarction, leading to loss of pituitary function.
• Hypothalamic lesions: As mentioned earlier, hypothalamic lesions can also affect the pituitary by causing a deficiency of pituitary hormone–releasing factors. In contrast to diseases that involve the pituitary directly, hypothalamic abnormalities can also diminish the secretion of ADH, resulting in diabetes insipidus (discussed later). Hypothalamic lesions that cause hypopituitarism include tumors, which may be benign (e.g., craniopharyngioma) or malignant; most of the latter are metastases from tumors such as breast and lung carcinoma. Hypothalamic insufficiency may also appear following irradiation of the brain.
• Inflammatory disorders and infections, such as sarcoidosis or tuberculous meningitis, can involve the hypothalamus and cause deficiencies of anterior pituitary hormones and diabetes insipidus.
• Genetic defects: Congenital deficiency of transcription factors required for normal pituitary function is a rare cause of hypopituitarism. For example, mutation of the pituitary-specific gene PIT1 results in combined pituitary hormone deficiency, characterized by deficiencies of GH, prolactin, and TSH.

Question 52

The clinical manifestations of anterior pituitary hypofunction vary depending on the specific hormones that are lacking.

Answer 52

• Children can develop growth failure (pituitary dwarfism) due to growth hormone deficiency.
• Gonadotropin (LH and FSH) deficiency leads to amenorrhea and infertility in women and decreased libido, impotence, and loss of pubic and axillary hair in men.
• TSH and ACTH deficiencies result in symptoms of hypothyroidism and hypoadrenalism, respectively, and are discussed later in this chapter.
• Prolactin deficiency results in failure of postpartum lactation.
• The anterior pituitary is also a rich source of melanotropins (also known as melanocyte-stimulating hormone), synthesized from the same precursor molecule that produces ACTH; therefore, one of the manifestations of hypopituitarism includes pallor due to a loss of stimulatory effects on melanocytes.

Question 53

Clinically relevant posterior pituitary syndromes

Answer 53

Diabetes insipidus. ADH deficiency causes diabetes insipidus, a condition characterized by excessive urination (polyuria) due to an inability of the kidney to resorb water properly from the urine. Diabetes insipidus can occur in a variety of conditions, including head trauma, tumors, inflammatory disorders of the hypothalamus and pituitary, and surgical complications. Diabetes insipidus from ADH deficiency is designated as central to differentiate it from nephrogenic diabetes insipidus, which is a result of renal tubular unresponsiveness to circulating ADH. The clinical manifestations of these two disorders are similar and include the excretion of large volumes of dilute urine with a lower than normal specific gravity. Serum sodium and osmolality are increased by the excessive renal loss of free water, resulting in thirst and polydipsia.

Syndrome of inappropriate ADH (SIADH) secretion. ADH excess causes over-resorption of free water, resulting in hyponatremia. The most frequent causes of SIADH are the secretion of ectopic ADH by malignant neoplasms (particularly small-cell carcinoma of the lung), drugs that increase ADH secretion, and a variety of central nervous system disorders, including infections and trauma. The clinical manifestations of SIADH are dominated by hyponatremia, cerebral edema, and resultant neurologic dysfunction. Although total body water is increased, blood volume remains normal, and peripheral edema does not develop.

Question 54

Craniopharyngioma

A small minority of these lesions occurs within the sella, but most are suprasellar, with or without intrasellar extension. A x age distribution is observed

Macroscopically more commonly they are x and sometimes x.

Answer 54

A small minority of these lesions occurs within the sella, but most are suprasellar, with or without intrasellar extension. A bimodal age distribution is observed, with one peak in childhood (5 to 15 years) and a second peak in adults 65 years of age or older.
adamantinomatous craniopharyngioma (most often observed in children) and papillary craniopharyngioma (most often observed in adults). adamantinmomatous radiologically demonstrable calcifications; the papillary variant calcifies only rarely.

more commonly they are cystic and sometimes multiloculated.

Question 55

Progressive Multifocal Leukoencephalopathy

PML is an encephalitis caused by the x;

Answer 55

JC polyomavirus; because the virus preferentially infects oligodendrocytes, demyelination is its principal pathologic effect.

The disease occurs almost exclusively in immunosuppressed individuals in various clinical settings, including chronic lymphoproliferative or myeloproliferative illnesses, immunosuppressive chemotherapy (including monoclonal antibody therapy targeting certain integrins), granulomatous diseases, and AIDS.

Question 56

Neurocysticercosis

Answer 56

Neurocysticercosis is caused by the CNS infection with the pork tapeworm Taenia solium, which is endemic in most low-income countries where pigs are raised. This form of cysticercosis is a relevant cause of seizures in endemic areas.

Question 57

ADEM. What is it? Age group?

Answer 57

Acute disseminated encephalomyelitis is a diffuse, monophasic demyelinating disease that follows a viral infection or, rarely, a viral immunization. Symptoms typically develop 1 or 2 weeks after the antecedent event and include headache, lethargy, and coma rather than focal findings, as seen in MS; in contrast to MS, all brain lesions appear similar, consistent with the clinically monophasic nature of the disorder. The clinical course is rapid, and as many as 20% of those affected die; the remaining patients usually recover completely.

Typically, acute disseminated encephalomyelitis presents in children or adolescents (usually younger than 15 years of age). However, cases have been reported in all ages

Question 58

Tumefactive demyelinating lesion

Answer 58

Tumefactive demyelinating lesion (TDL), also sometimes referred to as monofocal acute inflammatory demyelination (MAID), is a locally aggressive form of demyelination, usually manifesting as a solitary lesion (or sometimes a couple of lesions) greater than 2 cm that may mimic a neoplasm on imaging.

On imaging, they usually present with relatively little mass effect or surrounding oedema, contrast enhancement in an open-ring pattern, high ADC values, and low relative cerebral blood volume (rCBV).

Most do not progress to multiple sclerosis . In some instances, patients can deteriorate rapidly and succumb to illness (e.g. acute malignant Marburg variant of MS).

Question 59

Central pontine myelinolysis

Answer 59

Central pontine myelinolysis is an acute disorder characterized by loss of myelin in the base of the pons and portions of the pontine tegmentum, typically in a roughly symmetric pattern. It most commonly arises 2 to 6 days after rapid correction of hyponatremia, although it can also be associated with other severe electrolyte disturbances or osmolar imbalances, and is clinically known as osmotic demyelination syndrome. It appears that rapid increases in osmolality damage oligodendrocytes through uncertain mechanisms. Inflammation is absent from the lesions, and neurons and axons are well preserved.

Although it can involve most parts of the brain, periventricular and subpial regions are spared, and it is extremely rare for the process to extend below the pontomedullary junction. The clinical presentation is a rapidly evolving quadriplegia, which may be fatal or lead to severe long-term deficits, including the “locked-in” syndrome, in which patients are fully conscious yet unresponsive. It is imperative that hyponatremia be corrected slowly and carefully to prevent this tragic complication.

Question 60

Posterior Reversible Encephalopathy Syndrome

Answer 60

neurotoxic state that occurs secondary to the inability of the posterior circulation to autoregulate in response to acute changes in blood pressure. Hyperperfusion with resultant disruption of the blood-brain barrier results in vasogenic oedema, usually without infarction, most commonly in the parieto-occipital regions.

Question 61

Pleomorphic xanthoastrocytomas (PXA) are an uncommon circumscribed astrocytic tumour found in young patients and can be WHO grade 2 or 3.

They most often appear as x(location) tumours with a x component and x contrast enhancement, most commonly in the x lobe.

Features of slow growth may be present, such asx. x are rare.

Answer 61

Pleomorphic xanthoastrocytomas (PXA) are an uncommon circumscribed astrocytic tumour found in young patients and can be WHO grade 2 or 3.

They most often appear as cortical tumours with a cystic component and vivid contrast enhancement, most commonly in the temporal lobe where they present with temporal lobe epilepsy.

Features of slow growth may be present, such as no surrounding oedema and scalloping of the overlying bone. A reactive dural involvement expressed by a dural tail sign can be found. Calcifications are rare.

Question 62

DNET

Dysembryoplastic neuroepithelial tumours (DNET) are x (WHO Grade x) slow growing glioneuronal tumours arising from x.

They characteristically cause x

Answer 62

Dysembryoplastic neuroepithelial tumours (DNET) are benign (WHO Grade 1) slow growing glioneuronal tumours arising from either cortical or deep grey matter.

The vast majority are centred in cortical grey matter, arise from secondary germinal layers, and are frequently associated with cortical dysplasia (in up to 80% of cases).

They characteristically cause intractable focal seizures (see temporal lobe epilepsy).

Question 63

Multinodular and vacuolating neuronal tumours (MVNT) appear as small ‘x’ indolent x tumours that sometimes present with x.

These tumours have been most frequently identified in the x lobe, although that is likely to be due to that location being more likely to result in seizures than necessarily a predilection for that lobe.

Answer 63

Multinodular and vacuolating neuronal tumours (MVNT) appear as small ‘bubbly’ indolent subcortical tumours that sometimes present with seizures. These tumours have been most frequently identified in the temporal lobe, although that is likely to be due to that location being more likely to result in seizures than necessarily a predilection for that lobe.

DDX DNET, gangliocytoma

Question 64

Gangliocytomas are rare indolent CNS tumours (WHO grade x), primarily encountered in x, and frequently discovered as the cause of epilepsy.

On imaging, these tumours are usually characterised by x solid lesions with little associated mass effect and minimal or no surrounding vasogenic oedema.

Answer 64

Gangliocytomas are rare indolent CNS tumours (WHO grade 1), primarily encountered in children, and frequently discovered as the cause of epilepsy.

On imaging, these tumours are usually characterised by cortical solid lesions with little associated mass effect and minimal or no surrounding vasogenic oedema. Calcification and cyst formation can occur, and contrast enhancement is generally present.

Question 65

Dysplastic cerebellar gangliocytoma (Lhermitte-Duclos disease)

WHO x

Answer 65

WHO 1

rare tumour of the cerebellum appearing as thickening and increase in T2 signal of the cerebellar folia giving this lesion a characteristic striated appearance.

MRI: Widened cerebellar folia with a striated/tigroid appearance.

A number of associated conditions have been described 1,3, including:

Cowden syndrome (as part of COLD syndrome)
disorders of cortical formation
megalencephaly
grey matter heterotopia
polymicrogyria
polydactyly
hydromyelia
macroglossia
localised gigantism
leontiasis ossea

Question 66

Central neurocytomas are WHO grade x neuroepithelial x(location) tumours

Imaging features…

Answer 66

Central neurocytomas are WHO grade 2 neuroepithelial intraventricular tumours with fairly characteristic imaging features, appearing as heterogeneous masses of variable size and enhancement within the lateral ventricle, typically attached to the septum pellucidum. They are typically seen in young patients and generally have a good prognosis provided a complete resection can be achieved.

Calcification is seen in over half of cases, usually punctate in nature. Cystic regions are frequently present, especially in larger tumours. Contrast enhancement is usually mild to moderate. Accompanying ventricular dilatation is often present.

Question 67

Choroid plexus papillomas are intraventricular tumors that are most common in x(age group), in whom they tend to occur in the x(location); in x(age group), they more frequently involve the x(location).

Clinically, choroid plexus papillomas usually present with x due to

The far rarer choroid plexus carcinomas resemble adenocarcinoma; these tumors are almost always found in x(age group), where metastatic carcinoma is not typically encountered.

Answer 67

Choroid plexus papillomas are intraventricular tumors that are most common in children, in whom they tend to occur in the lateral ventricle; in adults, they more frequently involve the fourth ventricle.

Clinically, choroid plexus papillomas usually present with hydrocephalus due to obstruction of the ventricular system by tumor or overproduction of CSF.

The far rarer choroid plexus carcinomas resemble adenocarcinoma; these tumors are almost always found in young children, where metastatic carcinoma is not typically encountered.

Question 68

Marchiafava-Bignami disease (MBD) is a rare CNS disorder usually seen in the context of x and x. The condition classically involves x

Answer 68

Marchiafava-Bignami disease (MBD) is a rare CNS disorder usually seen in the context of alcoholism and malnutrition.

The condition classically involves necrosis and demyelination of the corpus callosum.

Question 69

Epidermoid cyst location vs arachnoid cyst

Answer 69

intradural: 90%
- cerebellopontine angle: 40-50% 2,8
- third most common cp angle mass, after schwannomas and meningiomas
- suprasellar cistern: 10-15%
- fourth ventricle: ~17%
- middle cranial fossa
- interhemispheric: < 5%
- spinal (rare)

extradural: 10%

Arachnoid cysts can occur anywhere within the central nervous system, most frequently (50-60%) located in the middle cranial fossa

Question 70

Haemangioblastomas are tumours of vascular origin and occur both sporadically and in patients with x. They are WHO grade x tumours, which can occur in the central nervous system or elsewhere in the body, including kidneys, liver, and pancreas.

These tumours generally present on imaging as x

x% in the posterior fossa

Answer 70

Haemangioblastomas are tumours of vascular origin and occur both sporadically and in patients with von Hippel Lindau disease. They are WHO grade 1 tumours, which can occur in the central nervous system or elsewhere in the body, including kidneys, liver, and pancreas.

These tumours generally present on imaging as sharply demarcated homogeneous masses composed of a cyst with non-enhancing walls, a mural nodule which vividly enhances, often with prominent serpentine flow voids.

95% in the posterior fossa

Question 71

Schizencephaly x

Answer 71

Schizencephaly is a rare cortical malformation that manifests as a grey matter lined cleft extending from the ependyma to the pia mater.

Question 72

Polymicrogyria

Answer 72

Polymicrogyria is one of many malformations of cortical development (see classification system for cortical malformations), and along with grey matter heterotopias, falls under a group of conditions characterised by abnormalities both in the migration of neurones to the cortex and abnormal cortical organisation.