sensory motor system extrinsic and intrinsic
Extrinsic compression(A) involves the sacral dermatomes whereas an intrinsic lesion (B) may result in sacral sparing. Syringomyelia This rare condition, in which a CSF-ï¬lled cavity (syrinx) develops centrally in the spinalcord (Fig. 15.4), also produces characteristic motor and sensory deï¬cits (Fig.15.5).peciï¬c cord syndromes Extrinsic vs. intrinsic lesions Extrinsic compression of the spinal cord, e.g. by tumour or prolapsed intervertebral disc, typicallyproduces a pattern of sensory loss in which thesacral dermatomes are involved (saddle anaesthe-sia).