Trans Synaptic Degeneration

In trans-synaptic degeneration or transneuronal atrophy, those neurons that lose their chief or only afferent connection (that is, their synaptic input) atrophy. Particular sites of trans-synaptic neuronal atrophy are (a) the lateral geniculate bodies following degeneration of the ganglion cells of the retina, optic nerve, or optic tract;

FIGURE 2.13

Anterograde or Wallerian degeneration. A. Lacunar infarct in the internal capsule. B. Degeneration of the ipsilateral pyramidal tract in the medulla (myelin stain). C. MRI of a 68-year-old man showing an old infarct in distribution of middle cerebral artery. Note the atrophy of the ipsilateral pedunculus due to wallerian degeneration of the descending corticopontine and pyramidal tracts.

FIGURE 2.13

Anterograde or Wallerian degeneration. A. Lacunar infarct in the internal capsule. B. Degeneration of the ipsilateral pyramidal tract in the medulla (myelin stain). C. MRI of a 68-year-old man showing an old infarct in distribution of middle cerebral artery. Note the atrophy of the ipsilateral pedunculus due to wallerian degeneration of the descending corticopontine and pyramidal tracts.

FIGURE 2.14

Wallerian degeneration. Degeneration of the fasciculus graci-lis from compression of the sensory nerve roots by a meta-static carcinoma in the lumbar spine (myelin stain).

FIGURE 2.14

Wallerian degeneration. Degeneration of the fasciculus graci-lis from compression of the sensory nerve roots by a meta-static carcinoma in the lumbar spine (myelin stain).

(b) the mammillary body following degeneration of the fornix (Fig. 2.15); and (c) the neurons of the gracile and cuneate nuclei of the medulla following degeneration of the posterior columns in the spinal cord.

FIGURE 2.15

Trans-synaptic atrophy of the mammillary body. A 58-year-old known hypertensive man suffered a stroke 7 years prior to his death. A. Transverse section reveals a large infarct in the right Ammon horn, hippocampus, and fusiform gyrus. The right fornix, the most prominent efferent connection to the mammillary body, is degenerated (wallerian degeneration). The right mammillary body, not included in the picture, is severely atrophic (trans-synaptic atrophy; myelin stain).

FIGURE 2.15

Trans-synaptic atrophy of the mammillary body. A 58-year-old known hypertensive man suffered a stroke 7 years prior to his death. A. Transverse section reveals a large infarct in the right Ammon horn, hippocampus, and fusiform gyrus. The right fornix, the most prominent efferent connection to the mammillary body, is degenerated (wallerian degeneration). The right mammillary body, not included in the picture, is severely atrophic (trans-synaptic atrophy; myelin stain).

olivary nuclei atrophy when the Purkinje cells in the contralateral cerebellar cortex have degenerated.

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