20: Sensory and motor changes

Sensory and motor changes

SENSORY CHANGES

Normal facial sensation, mediated by the trigeminal nerve, is important to protect the skin, mucosae and especially the cornea of the eye from damage. Facial sensory changes, which can be caused by lesions of a sensory branch of the trigeminal nerve or the central connections (Fig. 20.1), may lead to sensory awareness that is:

Sensory defects may lead to unrecognized damage from trauma or burns (‘trophic lesions’), and are occasionally associated with hyperaesthesia (i.e. the patient has a decreased sensory perception, but when sensation is perceived, it may cause discomfort).

AETIOLOGY AND PATHOGENESIS

Causes of lesions affecting the trigeminal nerve are shown in Boxes 20.1 and 20.2.

EXTRACRANIAL CAUSES

Extracranial causes of facial sensory loss are most common and include damage to the trigeminal nerve from the following causes.

Trauma

This is the usual cause of sensory loss – especially after orthognathic or cancer surgery. Ipsilateral hypoaesthesia or anaesthesia usually result. If the nerves are stretched or compressed (neuropraxia), there is often only hypoaesthesia, and recovery of sensation is speedy, typically within days. However, if the nerves are severed (neurotmesis), anaesthesia is profound and recovery is delayed for months accompanied by paraesthesia or hyperaesthesia. Recovery is sometimes not complete: repair may be indicated:

image Trauma to the mandibular division can have a variety of causes:

image Trauma to the mental nerve can have a variety of causes:

image Trauma to the lingual nerve can arise especially during resections or removal of lower third molars, particularly when the lingual split technique is used.

image Trauma to branches of the maxillary division of the trigeminal nerve may be caused by direct trauma or fractures (usually Le Fort II or III middle-third facial fractures) or surgery.

Intracranial lesions

Intracranial lesions affecting the trigeminal nerve or connections are uncommon but often serious.

Causes include:

image Trauma including surgical treatment of trigeminal neuralgia.

image Inflammatory disorders:

image Neoplasms, such as brain tumours (often metastases).

image Cerebrovascular disease:

image Brainstem lesions that may involve the fifth nuclei and central connections include brainstem:

image Cerebellopontine angle lesions that can compress the trigeminal nerve and as they enlarge, affect the neighbouring seventh and eighth nerves, producing facial weakness and deafness include:

image Petrous temporal bone lesions may cause pain and also affect the sixth nerve (Gradenigo’s syndrome) and include the following.

Jan 9, 2015 | Posted by in Oral and Maxillofacial Pathology | Comments Off on 20: Sensory and motor changes
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