Neuromodulation and neurostimulation are close cousins, but they are not the same thing.
Wikipedia defines neuromodulation as the application of an electrical, mechanical or chemical stimulus to a nerve, nerve complex or the brain to moderate activity and return it to a more normal state. For example, neuromodulation could be used to treat epilepsy and reduce the number or severity of seizures. In ophthalmology, we might use neuromodulation to treat hemifacial muscle spasms, severe symptomatic blepharospasm or trigeminal neuralgia. The goal would be to downregulate the afferent and/or efferent