It is compressing the spinal cord from its lateral or anterolateral aspect
causing impairment of pain and temperature sensation on the contralateral
side to the Schwannoma, with weakness, spasticity and loss of propriocep-
tion and vibratory sense on the ipsilateral side to the tumor. Damage to the
anterolateral system (ALS; spinothalamic tract) of the spinal cord causes
impairment or loss of pain and temperature sensation contralateralto the
lesion, and damage to the corticospinal tract in the spinal cord (lateral cor-
ticospinal tract; LCST) results in upper motor neuron syndrome ipsilateral
to the lesion. This is classical Brown-Sequard syndrome.
197.The answer is a.(Alberts, p 1072. Kasper, pp 303, 311–313. Kumar,
pp 1260–1262.)In pemphigus, autoantibodies to desmogleins (a member
of the cadherin protein family) result in disruption of the macula adherens
or desmosomes. The desmogleins are the transmembrane linker proteins
of the desmosome. Specific desmogleins are the target of the autoanti-
bodies in different forms of the disease. Cadherins are Ca^2 +-dependent
transmembrane-linker molecules essential for cell-cell contact, so their dis-
turbance in pemphigus leads to severe blistering of the skin because of dis-
rupted cell-cell interactions early in the differentiation of the keratinocyte
(epidermal cell) and excessive fluid loss. Hemidesmosomes (answer b)
contain different proteins than desmosomes and are not affected in pem-
phigus. Therefore, the basal layer of the epidermis remains attached to the
basal lamina in pemphigus. In contrast, in bullous pemphigoid (BP), anti-
gens develop that are specific for the hemidesmosomes. In that disease the
entire epithelium separates from the basal lamina. For more details on
junctional complexes, see the table in feedback for question 199.
198.The answer is c.(Kierszenbaum, pp 301, 303. Kasper, pp 291–292.
Kumar, pp 1256–1257.)Psoriasis is a chronic disease that affects both the
epidermis and dermis of the skin. There is hyperplasia of the epidermis and
abnormal microcirculation in the dermis as venules predominate in the
capillaries resulting in increased extravasation of inflammatory cells. Thus,
the underlying cause is the infiltration of inflammatory cells into the der-
mis with further migration of neutrophils into the epidermis. Those inflam-
matory cells release cytokines that induce an inflammatory response. There
is hyperplasia of the epidermis (answer a)as keratinocytes traverse the cell
cycle in a shorter period of time (answer b).Microabcesses form in the epi-
dermis(answer d)and epithelia are avascular (answer e).
Integumentary System Answers 309