?para-anti-ferro-dia-super

Q.All substances enhances  the effective magnetic field B_eff except

a.paramagnetic

b.antiferromagnetic

c.ferromagnetic

d.superparamagnetic

e.diamagnetic

ANS.---e

Any material, when placed into a constant magnetic field, responds by generating its own magnetic field. The magnetic susceptibility of a substance (or tissue) describes this magnetic response. Diamagnetic materials respond to an applied field with a very weak induced field (approximately10^-6 × the magnitude of the applied field) and in a vector direction that opposes that of the applied field. Paramagnetic materials have a larger induced field (approximately10^-2 to 10^-4 × the magnitude of the applied field), which is in the same vector direction as the applied field. Superparamagnetic and ferromagnetic materials generate a very large induced field, equal to or even greater than the applied field, and, as with paramagnetic substances, the induced field is in the same vector direction as the applied field.

Diamanetic substance reduces  the effective magnetic field B_eff.

IS IT REALLY EMPTY?

Q.All are true regarding “empty sella turcica” except

a. severely flattened pituitary gland

b. the superior portion of the sella turcica filled with CSF

c. the diaphragma sella  thin

d. enlargement of the sella turcica

e.abnormally positioned stalk

ANS ---e

It is the deficiency of the diaphragma that is the primary defect in “empty sella turcica”. This allows the suprasellar cistern to herniate into the sella, exposing it to CSF pulsation and eventually resulting in enlargement of the sella turcica.

The only differential diagnosis is that of an arachnoid cyst occupying the superior portion of the sella turcica. It is important to determine the position of the pituitary stalk to distinguish these entities. In the empty sella, the stalk is normal in position, whereas space-occupying cysts cause it to be obliterated or displaced

? HEMICORD

Q.All are true regarding diastematomyelia except

a.coronal clefting of spinal cord

b.80 % cases in female

c.45% cases in lumbar/lumbosacral area

d. the smaller hemicord often lies ventral to the larger hemicord

e.conus medullaris usually low

ANS----a

Diastematomyelia signifies a sagittal clefting of the spinal cord, conus medullaris, and/or filum terminale into two hemicords

The two hemicords are each narrower than normal  and nearly always (91%) reunite distally into a re-formed cord below the cleft . In 30% of cases the hemicords are grossly asymmetric in size. When the hemicords are asymmetric, the cord above and below the cleft is usually asymmetrically smaller on the side of the smaller hemicord, and the smaller hemicord often lies ventral to the larger hemicord. The filum terminale is usually-perhaps always-thickened and may itself tether the reunited cord. Hydromyelia is present in up to 50% of cases of diastematomyelia. It may affect the cord above the cleft and extend into one or both hemicords