Clinical Neurology for Psychiatrists, 6th Edition

FIGURE 2-19 n A, A standard spinal cord histologic preparation
stains normal myelin (white matter) black and leaves the
central H-shaped column gray. B, In combined system disease
(vitamin B12 deficiency), posterior column and corticospinal
tract damage causes their demyelination and lack of stain. C,
In tabes dorsalis (tertiary syphilis), damage to the posterior
column leaves them unstained. D, Multiple sclerosis (MS)
leads to asymmetric, irregular, demyelinated unstained
plaques.
system disease (B12 deficiency, see Chapter 5),
Friedreich’s ataxia, and the SCAs, each damages the
posterior columns alone or in combination with other
tracts. In these conditions, impairment of the posterior
columns leads to a loss of position sense that prevents
affected people from being able to stand with their
eyes closed (Romberg’s sign). When they walk, this sensory
loss produces a steppage gait (Fig. 2-20). In another
example, human T-lymphotropic virus type 1 (HTLV–1)
myelopathy (see Chapter 15), a common illness in
Central Nervous System Disorders 17
FIGURE 2-20 n The steppage gait consists of each knee being
excessively raised when walking. This maneuver compensates
for a loss of position sense by elevating the feet to
ensure that they will clear the ground, stairs, and other
obstacles. It is a classic sign of posterior column spinal cord
damage from tabes dorsalis. However, peripheral neuropathies
more commonly impair position sense and lead to this
gait abnormality.
which an infective agent predominantly attacks the
lateral columns, patients develop spastic paraparesis
that resembles MS.
Most important, myelopathy is associated with
dementia because of concomitant cerebral damage in
several illnesses. Examples of this association include
tabes dorsalis, combined system disease, AIDS, and,
when disseminated throughout the cerebrum, MS.