When the Franco-Prussian War broke out in 1870, he went to serve as a doctor with the Red Cross, where he earned a medal for Unusual Bravery.
His thesis for medical school was on optic neuritis in acute meningitis in children, which earned him respect and recognition in the field.
His other fields of work included multiple sclerosis, ophthalmoplegic migraine, hysteria, supranuclear lesions, and concomitant squint; all in the realm of neurology.
He is well known for the medical term Parinaud's syndrome, which is, "a dorsal midbrain lesion such as pinealoma which results in vertical gaze palsy, convergence-retraction nystagmus and light-near dissociation".
[2] Another medical condition named after him is Parinaud's oculoglandular syndrome (fever, papillar conjunctivitis and lymphadenopathy), a rare manifestation of cat scratch disease (caused by the bacteria Bartonella), which he was first to describe.