I am working on a project related to benign anisocoria (asymmetry in pupil size). Research indicates that activation of the sympathetic nervous system at the cortical level is asymmetric, with right hemisphere dominance. Given that premise, should the left or right pupil more often be larger, given greater sympathetic activation from the right hemisphere?
In this issue, discussions continue, especially regarding the lateralization of cerebral hemispheric monitoring of the tone of the parasympathetic system.
Most scientists are inclined towards the dominant control of the right hemisphere of the tone of the sympathetic system.
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In my opinion, you should backtrack the whole sympathetic chain and look for crossing fibres. The peripheral component arises from the stellate ganglion and mounts along with the internal carotid artery. (Hence Horner's syndrome in carotid artery dissection.) The spinal component is mediated by the tractus intermediolateralis, situated in the thoracic myelon. (for the pupil, level about Th2/3). In lesions of the dorsolateral medulla oblongata, there is Horner's syndrome, too. All these sympathetic groups are thus ipsilateral. As far as I remember, the central pathways colocalize with the pyramidal tract, but there should be a crossing above the level of the decussatio pyramidarum.
If the association between Cluster headache and ipsilateral hypothalamic activation and consequent ptosis is correct, there is another ipsilateral localisation to consider.
Consider as well that sympathetic failure may not be absolute, rather these systems are intermingled with each other, and at least the arousal system as well.
Hope this helps, as your project is ambitious and interesting as well.
