Targeted Drug Delivery (Intrathecal and Intracranial) for Treatment of Facial Pain.

Despite the high incidence of facial pain, targeted drug delivery remains a rarely used technique for treatment of otherwise refractory pain. Two distinct paths have been described. The intraventricular route allows direct access to intracerebral opioid receptors. The more recently introduced upper cervical or cisternal intrathecal route, is based on the same theories as classical intrathecal route. Intraventricular route was first described by A.K. Ommaya; its use remains limited, mostly with morphine, despite a high clinical efficiency, probably because of the invasive nature of the procedure and the need for daily direct injections. The ability to connect the catheter to an implantable pump may help to facilitate the acceptance of this approach. The also rarely used high cervical intrathecal or cisternal route is very efficient, because facial pain signals are transmitted mainly via the trigeminal nerve roots and synapse on the second-order neurons in an area that extends from the lower brainstem to the C1 and C2 levels of the spinal cord. The risks of cervical puncture may explain the rarity of its use. However, new devices allowing a simpler lumbar approach and the ongoing opioid crisis are the factors that may facilitate the wider use of this effective technique for the treatment of facial pain.