Is there variable neuronal susceptibility to compression?

Chung Yee Chung,Evan Po-Fat Yiu

doi:10.35119/asjoo.v16i3.421

Abstract

A 12-year-old boy with suprasellar germinoma complicated by hydrocephalus was found to have dorsal midbrain syndrome and bilateral compressive optic neuropathy. Following a third ventricular neuroendoscopic biopsy and the initiation of chemotherapy, a follow-up magnetic resonance imaging scan of the brain showed significant regression of the tumor with resolution of hydrocephalus. On smooth pursuit, there was significant improvement in upgaze. However, light-near dissociation of his pupillary defect was persistent. Fundal examination showed persistent temporal pallor of the optic discs bilaterally, associated with a suboptimal best-corrected visual acuity of 20/40 and bilateral centrocecal scotoma.The differential recovery of neuronal function following relief of compression is poorly understood. In this case, both the optic nerve and pretectal axonal fibers responsible for pupillary reflex, with their neuronal cell bodies residing outside the direct compressive site at the midbrain, showed poor functional recovery. However, relief of pressure at the rostral interstitial medial longitudinal fasciculus and posterior commissure nuclear complexes resulted in significant clinical improvement in upgaze. This case suggests that, for neurons, axons are apparently more susceptible to pressure than cell bodies. The predominant transmission of nerve impulses takes place through the length of axons, and thus is more sensitive to pressure changes, with the associated microvascular compromise and demyelination. 

Highlights

Of all germinomas which occur in the central nervous system, 25%-35% are found in the suprasellar region.[1]
It is generally believed that neurons of the central nervous system have limited regenerative capacity, patients with this condition may improve following the treatment for hydrocephalus.[3]
We described the evolution of clinical signs following the treatment of a suprasellar germinoma

Summary

Introduction

Of all germinomas which occur in the central nervous system, 25%-35% are found in the suprasellar region.[1]. Of all germinomas which occur in the central nervous system, 25%-35% are found in the suprasellar region.[1] Obstruction of the flow of cerebrospinal fluid, with subsequent hydrocephalus and dilatation of the aqueduct of Sylvia by the tumour is a known cause of dorsal midbrain syndrome.[2] Even within the constellation of clinical signs comprising the dorsal midbrain syndrome, some features may resolve better than the others.

Results

Conclusion