An update on the causes, assessment and management of third division sensory trigeminal neuropathies

Introduction:
Sensory neuropathies of the mandibular division of the trigeminal (V3) nerve can be debilitating, causing difficulty with daily function. It has a variety of causes, including iatrogenic injury, usually caused by third molar removal, local anaesthetic administration, implant placement or endodontic treatment. Non-iatrogenic causes include infection, primary or secondary neoplasia and various medical conditions.

Objective:
To review the aetiology, evaluation and management of V3 neuropathy in a retrospective case-series of patients referred to a specialist nerve injury clinic over an eight-year period, particularly focusing on the non-iatrogenic causes of this presentation.Methods A retrospective analysis of the case notes of 372 patients referred to the specialist nerve injury clinic between 2006 and 2014 was carried out to establish the cause of the neuropathy and subsequent management or referral. The assessment protocol of trigeminal neuropathy used in the clinic is also outlined.

Results:
Most patients (89.5%) presented with neuropathy due to iatrogenic injury. Of the non-iatrogenic causes (10.5%), malignancy accounted for a fifth of presentations, and infection almost two-fifths, demonstrating the importance of prompt identification of a cause and management by the clinician, or referral to the appropriate specialty. Other, more rare causes are also presented, including multiple sclerosis, sickle-cell anaemia and Paget's disease, highlighting the importance to the clinician of considering differential diagnoses.

Conclusions:
This case series demonstrates the less frequent, but nevertheless important, non-iatrogenic causes which clinicians should consider when assessing patients with trigeminal neuropathy.