refers to bilateral leg weakness. Paraparesis may occur with brain lesions,
spinal cord lesions in the thoracic area, and lumbosacral center lesions
(Figure 238.1 A-D). Brain and thoracic spine lesions may produce spastic
or flaccid paraparesis. Lumbosacral center lesions produce flaccid weakness.
Spastic weakness is characterized by increased muscle stretch reflexes,
strong leg recoil to a sudden intense pull, and sustained ankle clonus.
Flaccid weakness is characterized by decreased or absent muscle stretch
reflexes, weak leg recoil to sudden intense pull of the leg, and no ankle
Figure 238.1.— Possible sites of anatomical injury producing paraparesis: A: parasagittal region; B: bilateral periventricular regions; C: spinal cord below T1; D: lumbosacral center; V: ventricles; T: thalamus; FN: facial nerve; UQ: upper quadrant; LQ: lower quadrant; BP: brachial plexus; LSP: lumbosacral plexus. The colored rectangles indicate the location of weakness produced by damage to the various components of the somatic motor system.