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DIFFERENTIAL DIAGNOSIS OF LEG MONOPARESIS

Leg monoparesis usually presents in neonates as an inability to lift up the foot or the whole leg against gravity. The first step to determine the cause of leg monoplegia is to establish the anatomical location of the lesion (Figure 233.1 A-H).

Figure 233.1.— Schematic representation of the cortical component of the somatic motor system and sites of possible injuries causing leg monoparesis. The colored rectangles indicate the location of weakness produced by damage to the various components of the somatic motor system. V: ventricles; T: thalamus; UQ: upper quadrant; LQ: lower quadrant; FN: facial nerve; BP: brachial plexus; LSP: lumbosacral plexus. A: brain and midbrain; B: upper pons; C: lower pons and medulla; D: upper spinal cord above the brachial center; E: lower spinal cord below the brachial center but above the lumbosacral plexus; F: lumbosacral motor center; G: lumbosacral plexus; H: lower extremity peripheral nerves.

 
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lower extremity peripheral nerves lumbosacral plexus lumbosacral motor center lower spinal cord upper spinal cord lower pons and medulla upper pons brain to midbrain lumbosacral plexus brachial plexus facial nerve fibers to the lower facial quadrant fibers to the upper facial quadrant thalamus thalamus thalamus lateral ventricle lateral ventricle To identify a structure pause the pointer over the abbrevations, or the structure in question; to idenyify the sites of injury pause pointer over the letters; do not click. Not all structures are labeled. Figure must be centered.