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CHAPTER 23
The flexor-withdrawal reflex in incomplete lesions may be one-phased—i.e. the extremity
may not return to its original position—or it may do so (two-phase reaction). Therefore,
these reflex responses are not indicative of a distinction between complete transverse
lesions (one-phase response) and incomplete lesions. If not all supranuclear pathways
are interrupted and, especially, if the extrapyramidal tracts remain intact, voluntary
function below the level of the lesion is more or less preserved. The paresis is of spastic
type in extension.
Various observers have drawn attention to the occasional development of atrophy
of the hand muscles, in particular in the intrinsic muscles of the ringers in high cervical
or atlanto-axial lesions, which may lead to misinterpretation and diagnosis of amyo-
trophic lateral sclerosis or syringomyelia. The cause of this phenomenon lies in an
impairment of the blood supply at high cervical level. It must be remembered that most
of the vascular supply to the cervical cord runs down the anterior spinal artery originating
from the vertebral arteries. Therefore, very high cervical or atlanto-axial lesion, caused
by tumour or fracture, may block the arterial supply in these areas, resulting in impair
ment of the descending blood supply to the distal parts of the cervical cord and giving
rise to clinical symptoms of lower cervical level.
There exists a lamellar arrangement of the fibres within the pyramidal tracts (somato-
topic division) which accounts for the variations in extent of the supranuclear paralysis
affecting individual areas of the body. This is particularly conspicuous in incomplete
lesions of the cervical cord, where the pyramidal fibres for the upper limbs are situated
medially within the pyramidal tract area while the fibres for the lower limbs lie eccentric
ally and those for the trunk in the middle of the tract. This anatomical arrangement
explains the variations in spastic paresis involving various parts of the body, especially
in extramedullary tumours of the cervical cord. Symonds & Meadows (1937) described
in detail the clinical symptomatology of tumour compression of the cervical cord in the
neighbourhood of the foramen magnum. They found in four of their cases, where the
compression of the tumour was to one side of the midline, that the spastic paresis was
first noticeable in the ipsilateral upper limb followed by weakness of the ipsilateral lower
limb. However, in two of their cases they found, in confirmation of Elsberg's (1929)
experience, that the weakness of upper motor neuron type developed in the contralateral
lower limb. Moreover, in one of their cases, the weakness developed after lumbar punc
ture and was confined to the upper limbs and affected both equally, although the tumour
was situated laterally.
Such lamelliform arrangement also exists, as mentioned before, in the afferent tracts,
both the spinothalamic and posterior column tracts, which is also particularly apparent
in the cervical cord.
Incomplete lesions of the spinal cord may also affect autonomous mechanism. In
cervical lesions, fibres concerned with oculopupillary activity and originating in the hypo-
thalamus pass to the cilio-spinal centre of Ti and T2 segments through the anterolateral
tracts, in close relation to the pyramidal tracts. Unilateral cordotomy carried out above
Ti always results in Horner's syndrome of the ipsilateral side associated with disturbances
of vasomotor and sudomotor function and the same may occur in incomplete lesions of
the cervical cord as a result of fracture dislocations of the spine or tumours. There may
