Post-extraction inferior alveolar nerve neurosensory disturbances: A guide to their evaluation and practical management Item Type Article Authors Mahon, Nicola Citation Mahon, N (2014) Post-extraction inferior alveolar nerve neurosensory disturbances: A guide to their evaluation and practical management.Irish Dental Association. Oct. Publisher Irish Dental Association Journal Irish Dental Association Download date 25/09/2021 06:40:59 Link to Item http://hdl.handle.net/10147/333831 Find this and similar works at - http://www.lenus.ie/hse Peer-reviewed JOURNAL OF THE IRISH DENTAL ASSOCIATION Post-extraction inferior alveolar nerve neurosensory disturbances – A guide to their evaluation and practical management Précis: This paper focuses on the classification, causes, prevention, management, treatment options and prognosis of inferior alveolar nerve injuries, post dental extraction. Algorithms are provided to guide the practitioner on monitoring or referring these injuries and as to the pros and cons of surgery. Abstract: Inferior alveolar nerve injuries are a recognised complication of mandibular third molar extractions. This paper describes the different types of nerve injuries that may occur. A differential of possible causes is provided and an approach to the immediate and follow-up management is outlined. The prognosis of such injuries is reviewed so that patients can be informed of the possible postoperative outcome. The algorithm shows the timeline for monitoring/referring and the included tables outline the advantages and disadvantages of surgery versus watchful waiting. Journal of the Irish Dental Association 2014; 60 (5): 241-250. Introduction to eight weeks). The structure of the Neurosensory disturbances (NSDs) are a nerve remains intact but the conduction possible side effect of many dental impulses are interrupted by Dr Nicola Mahon MFDS MRCS treatments. This study is a review of the compression/ischaemia of the nerve. The National Maxillofacial Unit current literature on how to manage this sensory deficit is usually a mild St James’s Hospital complication. The purpose of this paper is to paraesthesia.4 A microsurgical Dublin 8 generate an understanding of the intervention is not indicated.5 mechanisms, causes, management and 2. Axonotmesis – A more severe form of Prof. Leo FA Stassen prognosis of nerve injuries. nerve injury. Recovery takes weeks to FRCS (Ed) FDS RCS MA FTCD years and occurs only by the regeneration Mechanism and classification FFSEM(UK) FFD RCSI of axons. There is disruption of the of nerve injuries Consultant Oral and neuronal axon with Wallerian Maxillofacial Surgery The possible mechanisms of neural injuries degeneration and yet the myelin sheath are mechanical, chemical and thermal remains intact. This injury is usually trauma.1 Nerve injuries were historically caused by a severe crush, contusion or Address for correspondence: classified by Seddon in 1943 based on three stretching of the nerve. The sensory Prof. Leo FA Stassen types of nerve fibre injury and whether there deficit is usually a severe paraesthesia.4 National Maxillofacial Unit, is continuity of the nerve.2 3. Neurotmesis – The most severe form of Dublin Dental School and Hospital, 1. Neurapraxia – The least severe form of nerve injury. There is internal disruption Lincoln Place, nerve injury, commonly resulting in of the architecture of the nerve with Dublin 2. temporary numbness/paralysis with perineurium and endoneurium Email: [email protected] subsequent complete recovery within involvement. If the nerve has been hours to months of the injury (average six completely divided, a neuroma may form October/November 2014 VOLUME 60 (5) : 241 Peer-reviewed JOURNAL OF THE IRISH DENTAL ASSOCIATION Table 1: Comparison between Seddon and Sunderland classifications. SEDDON 1943 SUNDERLAND 1951 Neurapraxia First-degree injury Perineurium Axonotmesis Second-degree injury Neurotmesis Third-degree injury – Endoneurium disruption Endoneurium but epineurium and perineurium intact Epineurium Fourth-degree injury – Perineurium injury with Nerve fibre only epineurium intact Fasciculus Fifth-degree injury – Complete transection Anatomy of a normal nerve fibre taken from Smith and Lung.3 at its proximal stump and Wallerian degeneration occurs at the Types of sensory nerve impairment distal stump. Causes of neurotmesis include a severe contusion, Sensory impairment may be transient or permanent. Nerve damage stretching, laceration, local anaesthetic (LA) toxicity, and can be subjectively described by patients as paraesthesia, transection. dysaesthesia, anaesthesia or pain.3,5,8,9 These injuries are likely to be permanent without repair or will only achieve partial recovery. The sensory deficit is characterised by Paraesthesia – represents abnormal sensations.10 It may be divided anaesthesia or dysaesthesia.4 Thus, a microsurgical intervention into spontaneous paraesthesia or elicited paraesthesia.11,12 Patients may be indicated.5 This classification was further developed by present with symptoms of “pins and needles”, “tingling”, “burning”, Sunderland in 1951.6 Sunderland’s classification subdivides “prickling”, “itchiness”, or “partial numbness”, which may not be neurotmesis into a further three divisions (Table 1). Both particularly unpleasant.1,3 classifications are still commonly referred to in the literature, but in light of advances in molecular biology, they now have their Dysaesthesia – Unpleasant abnormal sensation, whether spontaneous limitations. or evoked.3,11,12 It includes: The limitation with these classifications is that they only deal with the - hyperalgesia: exaggerated amplified response to a noxious anatomical disruption of neural tissue, which we can only presume as stimulous.3 we do not see the nerve unless we operate. However, other factors - allodynia: pain evoked by innocuous stimuli such as light touch or may be involved. When a surgical procedure has been performed, gentle pressure to deep tissue, not normally painful when applied neuronal plasticity occurs. This is the potential of the nervous system elsewhere in the body.11 to adapt to inputs by changing temporarily or permanently their biochemical, physiological, and morphological characteristics. Anaesthesia – Total absence of sensation, including pain or an Inflammation and injury occurs at the surgical site releasing insensitivity to all forms of stimuli that would normally be painful.3,11,12 inflammatory mediators, i.e., prostanoids, which, by activating Symptoms that are akin to post-dental injection anaesthesia. intracellular pathways, lower the threshold of nociceptors (peripheral sensitisation). This increased excitability of nociceptors can sweep back Pain – An unpleasant sensory and emotional experience, associated centrally to the dorsal horn nuclei of the central nervous system (CNS), with actual or potential tissue damage and/or described in terms of changing their protein structures, facilitating an increased number of such damage.12 ion channels. This increases excitatory transmitters and reduces –Neuroma pain:pain aggravated by mechanical stimulation.13 inhibitory transmitters, resulting in an abnormal perceptual response to Differential of the possible causes of nerve injury a normal sensory input (central sensitisation). This is usually reversible The extraction when the inflammation resolves, but if nerve injury has occurred, both It is estimated that 42.9-69% of all iatrogenic injuries to the inferior the injured neurons and their non-injured neighbours give action alveolar nerve (IAN) are caused by third molar surgery, especially potentials spontaneously – “etopic pacemaker activity”. those molars impacted in close proximity to the IAN.14,15 Renton Alterations in gene expression are produced and this changes the stated that nerve injury can be temporary in 8% of these cases and function of neurons. It may be reversible, or non-reversible. If the permanent in 3.6% of these cases.9,16 Rates of paraesthesia are quoted injured axon and its target are not re-opposed, unmylelinated axons as 0.4-8.4%.17,18,19,20,21,22 This may be caused by direct trauma to the start to die and sensory inflow is permanently disturbed.7 nerve (root elevators may cause blunt trauma to the nerve via October/November 2014 242 : VOLUME 60 (5) Peer-reviewed JOURNAL OF THE IRISH DENTAL ASSOCIATION Table 2: Factors which initiate or perpetuate disorders of neuronal tissue (systemic diseases which also cause neuropathies).1,10,42 Bacterial infections Viral infections Arthridities Neoplasia Metastases Haematological (herpes zoster) diseases (leukaemia and lymphoma) Multiple myeloma Cysts Metabolic disorders Vitamin deficiencies Alcohol abuse Drug-induced (diabetic diseases neuropathy) (chemonecrosis) Bone diseases Multiple sclerosis Sarcoidosis Epilepsy Collagen vascular Psychological (osteomyelitis) (seizure may have diseases disorders caused a fracture) compression or the nerve may be disrupted by rotating burs).20 It may Neurotoxicity of the local anaesthetic also be caused by indirect trauma via compression of the nerve, due If the LA is injected intrafascicularly, or is deposited in the nerve during to oedema or formation of a haematoma post extraction.23 A minor needle withdrawal, this can induce a localised chemical injury to the compression usually only causes a temporary conduction block (i.e., nerve.3 Smith and Lung explain how this results in demyelination, Seddon’s neuropraxia/Sunderland’s first-degree injury).24 Extraction of axonal degeneration and inflammation