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    Iatrogenic trigeminal nerve injuryMinimising and managing injuries inrelation to dental procedures

    The trigeminal nerve is the

    largest peripheral sensory nerve

    in the human body and is

    represented by over 40% of the

    sensory cortex. The nerve

    supplies the face, eyes, mouth

    and scalp with general sensation

    in three divisions (ophthalmic,

    maxillary and mandibular) and

    supplies the mastication muscle.

    In addition the most commonlyinjured trigeminal nerve

    branches, the inferior alveolar

    and lingual nerves are very

    different entities in that the

    lingual nerve sits loosely in soft

    tissue compared with the IAN

    that resides in a bony canal.

    Features of trigeminal nerve

    injury associated with dental

    procedures

    Both lingual and inferior

    alveolar nerve injuries are closedinjuries; unlike the open sensory

    nerve injuries seen mainly on

    limbs due to trauma, that makes

    them accessible to immediate

    exploration and repair by

    orthopaedic or plastic surgeons.

    Paradoxically our profession has

    a sit and wait policy for

    resolution of trigeminal nerve

    injuries unless it is known that

    section of the nerve has

    occurred.

    88% of lingual nerve injuriesassociated with conventional

    (lingual access) third molar

    surgery resolve thus lulling

    dentists into a false sense of

    security believing that all nerve

    injuries get better. This

    misconception has also led to

    the assumption that most

    inferior alveolar nerve injuries

    resolve when in fact they are

    predominantly permanent5

    .

    It would be difficult to

    traumatise a nerve with a drill

    without causing a multitude of

    events including;

    a)direct mechanical trauma (tear,

    section, crush, stretch etc)

    b) neural chemical trauma due

    to intracellular components

    released during trauma;

    haemoglobin irritates neural

    tissue

    c) ischaemic injury within a bony

    canal (IAN) with continued

    bleeding or scar formation.

    It is unlikely that damage will

    be a simple cut. It is more likely

    that it will involve a combination

    of events, providing a complex

    therapeutic challenge.

    If the patient suffers injury

    during an elective treatment that

    was supposed to improve their

    quality of life, any iatrogenic injury

    will distress both the patient and

    the clinician. The patients

    frustration is often compounded

    by poor management (Hopefully

    something that this article will

    reduce).

    Sensory nerve injuries

    frequently cause pain rather thannumbness. As the neuropathic

    area invariably involves the

    mouth and face the patients

    ability to eat, speak, drink, sleep,

    kiss, shave or apply makeup is

    often severely compromised.

    Due to the chemical and

    neurophysical changes in the

    injured sensory nerve, light touch

    or drafts of air can cause

    debilitating neuralgic pain

    (allodynia) or in some instances

    the patient might experienceconstant background pain. All of

    which can add to the patients

    distress.

    Complaints investigated by

    national registration bodies are

    predominantly related to implants

    and often involve IAN injury.

    Neuropathic pain can be very

    debilitating and, when

    compounded by poor

    management, may result in

    litigation.

    Current management ofthese nerve injuries is often

    inadequate. Although surgical

    correction may be offered there

    is little attention to medical or

    counselling intervention and

    there are often delays. A recent

    review of publications pertaining

    to trigeminal nerve repair

    highlights that the average time

    from injury to nerve exploration

    was 16 months; this is far too

    late to prevent central neural

    changes. Indeed after three

    months, permanent central and

    peripheral changes occur within

    the nervous system subsequent

    to injury that is unlikely to

    respond to surgical intervention6

    .

    A review of 183 injuries

    Renton and Yilmaz (2010)

    lingual nerve (n=93; 52%) LNI

    inferior alveolar nerve injuries

    (n=90; 47%) IANI

    buccal nerve (n=3; 1%) B.

    Injuries were regarded as being

    permanent if the patient had

    their symptoms for more than 3

    months. Many of the LNI and

    IANI patients had permanent

    injuries (63.4% and 54.8%,

    respectively) and females were

    more likely to suffer from

    permanent nerve injury

    (p>0.001). Only 12.9% and 5.4%

    of the LNI and IANI cases were

    temporary.

    Third molar surgery (TMS) and

    local anaesthesia caused the

    majority of IANIs and LNIs

    Approximately 70% of all

    patients presented withneuropathic pain, despite the

    additional presence of

    anaesthesia and/or paraesthesia.

    Causes of inferior alveolar

    nerve (IAN) injury in general

    practice

    (Ablative surgery, trauma and

    orthognathic surgery have not

    been included here).

    Local analgesia

    Injuries to inferior alveolar andlingual nerves are caused by local

    analgesia block injections and

    have an estimated injury

    incidence of between 1:26,762

    to 1:800,000 inferior alveolar

    nerve blocks7 8

    . More recently

    the incidence of nerve injury in

    relation to IDBs has been

    calculated as 1:609,000 but

    with a significant increase in

    injury rate with 4% agents9

    .

    Recovery is reported to takeplace at 8 weeks for 85-94% of

    cases10

    . IAN injuries may have

    a better prognosis than lingual

    nerve injuries but if the duration

    of nerve injury is greater than

    8 weeks then permanency is a

    risk. However, the true incidence

    is difficult to gauge without large

    population surveys.

    In the light of the current

    incidence of nerve injuries in

    relation to dental anesthesia

    warning of patients is not

    considered to be a routine

    requirement and indeed in the

    UK these iatrogenic injuries are

    not considered negligent.

    Claims which are the result of

    nerve injuries are the third

    largest group of claims in

    terms of frequency, behind

    endodontics and crown and

    bridgework

    They can also be very costly to

    resolve, especially when the

    patients occupation is such that

    the consequences of the nerveinjury interferes with the

    patients employment or

    income. Some of these injuries

    can profoundly affect the

    patients quality of life, and result

    in significant general damages

    for pain and suffering and

    similar grounds for compensation.

    This article has been abstracted

    from an original paper written by

    Tara Renton, Professor Oral

    Surgery Kings College London

    Dental Institute who is arecognised and experienced

    authority in this field. It looks at

    the causes and management of

    trigeminal nerve injuries.

    Trigeminal nerve injury is the

    most problematic consequence

    of dental surgical procedures

    with major dento-legal

    implications1

    . The incidence of

    lingual nerve injury has remained

    static in the UK over the last 30

    years, however the incidence ofinferior alveolar nerve (IAN) injury

    has increased; the latter being

    due to implant surgery and

    endodontic therapy.

    Iatrogenic injuries to the third

    division of the trigeminal nerve

    remain a common and complex

    clinical problem. Altered

    sensation and pain in the

    orofacial region may interfere

    with just about every social

    interaction we take for granted2

    .

    These injuries can have negative

    effects on the patients self-

    image and quality of life which

    can also produce significant

    psychological effects3

    .

    Tara Renton

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    However there is increasing

    evidence that higher

    concentration local anaesthetic

    agents may be associated with

    increased rates of neuropathy

    resulting in increasing litigation in

    the USA. A recent settlement of

    U$1.4 million dollars (Main USA)

    for lingual nerve injury caused by

    local analgesic inferior alveolar

    nerve block highlights the

    associated disability and social

    repercussions of these injuries.

    Causes of damage

    Direct mechanical trauma by

    the needle

    Chemical nerve injury due to

    LA components.

    The resultant nerve injury may

    be a combination of neural

    haemorrhage, inflammation and

    scarring resulting in

    demyelination.

    Articaine

    This amide analgesic was

    introduced to dentistry in 1998,

    however lignocaine (also an

    amide analgesic) remains the

    gold standard in the UK.

    Articaine is the most widely

    used local analgesic in many

    countries for over 20 years11 12

    .

    Articaine is said to have a

    number of advantages, namely;

    low toxicity subsequent to

    inadvertent intravascular injectionwhich may be due to the rapid

    breakdown to an inactive

    metabolite (Articainic acid), rapid

    onset of surgical analgesia (2.5

    =/-1.1 minutes) compared with

    conventional Lignocaine and

    better diffusion through soft and

    hard tissue. The conclusion

    drawn is