List three causes of coma with bilateral miosis. (15% marks)
Chris Nickson has done an awesome thing about this at LITFL. I have shamelessly ripped him off, because I have no access to Bhidayasiri's "Neurological differential diagnosis: a prioritized approach" which is given as his main reference.
Anyway. The more specific answer should mention that among focal neurological causes, bilateral lesions are required to cause bilateral miosis.
Thus, the corrected list of causes would resemble the following:
Causes of bilaterally small pupils which do not produce coma:
The whole "metabolic encephalopathy" thing is somewhat vague, and is included here because it is technically accurate. Metabolic encephalopathy can describe many things, and produce many signs.
A reader of LITFL had also pointed out that phenothiazines should be expected to cause mydriasis, by virtue of their anticholinergic effect. This is not the case. A 1973 article from California Medicine reports 48 cases of phenothiazine poisoning, in which the pupils were almost invariably small. This can be attributed to the alpha-antagonist effects of these drugs, which override the anticholinergic effects.
Specifically, the reader is directed to Coma and Small Pupils, aka Neurological Mind-boggler 002
Barry, Daniel, Frank L. Meyskens Jr, and Charles E. Becker. "Phenothiazine Poisoning A Review of 48 Cases." California medicine 118.1 (1973): 1.