Chapter 10
Neurological Disorders of the Head and Neck
Aim
This chapter reviews the common neurological problems that may present in the head and neck.
Outcome
After reading this chapter you should be able to describe the presenting features of common neurological conditions in the head, neck and mouth.
Introduction
Brain structure and function rarely feature prominently in the dental curriculum, but a knowledge of some basic features is helpful in understanding why patients can present with particular symptoms in particular conditions.
The cerebral cortex is the controlling centre in the brain, which initiates voluntary actions in the body and processes the sensory information flowing in from the peripheral nervous system. Between these two are a variety of brain areas that process and modify the information flowing into and away from the cortex. Dysfunction of specific brain areas gives symptoms with characteristic clinical patterns. One function of the cerebellum, for example, is to control and modify fine movement, therefore lesions in this area produce a tremor on voluntary movements but not at rest. Lesions in the substantia nigra, on the other hand, produce a tremor at rest that is lost on movement, predominantly seen in the limbs but also evident in the mandible.
Most of the cranial nerves leave the brain in the pons and the medulla. Lesions here will have orofacial consequences – for example, a facial weakness following a stroke. Some of the cranial nerves run close together in their intracranial course, and pathology of one may affect another. A neuroma of the acoustic nerve (VIII) can produce symptoms in the trigeminal (V) and the facial (VII) nerves. Thus the patient presenting to the clinician with unilateral facial weakness or numbness should be checked for deafness on the same side, which could suggest such a lesion.
Testing the cranial nerves is an important clinical skill, which can be mastered easily by all medical and dental practitioners. A basic test can be performed in less than a minute by an experienced practitioner (Table 10-1).
| Nerve | Name | Test |
| I | Olfactory | Not usually tested in the limited examination |
| II | Optic | Test each eye separately Can count fingers held 1m in front of the patient Visual fields tested by moving object into vision from four distinct points in the periphery with the patient’s gaze straight ahead Pupillary reflex contraction to light and dilation to close visual accommodation bilaterally (requires intact III) |
| III | Occulomotor | Tested with IV and VI Each eye can track a moving object smoothly up, down, left and right. When the eyes are tested together no double vision is reported near to the extremes of gaze or looking straight ahead Eyelid retraction occurs with upward gaze Pupillary responses listed in II also require intact III function. |
| IV | Trochlear | Tested with III Lesion produces weakness in upward and outward gaze on the affected side only |
| V | Trigeminal | Sensory to the face Test light touch and pinprick sensation (with cotton wool and a blunted needle) to each of the trigeminal branches on each side of the face Motor to the masticatory muscles Get the patient to clench the teeth onto an object (wood spatula) on first one side, then the other, with the examiner trying to remove the object each time |
| VI | Abducent | Tested with III. Lesion prevents lateral gaze on the affected side only |
| VII | Facial | Motor to the facial muscles Get the patient to:
|
| VIII | Acoustic | Hearing Cover one ear, whisper a word into the open ear and ask the patient to repeat the word. Repeat for the other ear Balance Stand the patient upright with their eyes closed and gently push the patient to one side. Balance should be maintained. If not, be prepared to steady the patient |
| IX | Glossopharyngeal | Tested with X Touch the back of the soft palate with an instrument. The patient should retch and elevate the soft palate |
| X | Vagus | Tested with IX |
| XI | Accessory | Get the patient to elevate their shoulders and then turn their head to each side against resistance provided by the examiner |
| XII | Hypopglossal | Get the patient to protrude the tongue. There should be no deviation to the side. If there is, the tongue deviates towards the weak side |
Neuromuscular problems of the head and neck of importance to the dental clinician include the following:
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movement disorders
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sensory loss
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motor loss.
Movement Disorders
Movement disorders involving the head and neck can make delivery of dental care difficult. Knowledge of the type of movement disorder and an appreciation that the patient has little or no control over the problem are important. The movement disorders of importance are:
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Cerebral palsy
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Parkinson’s disease.
Cerebral Palsy
Cerebral palsy is characterised by a fixed neurological defect that is thought to occur around the time of birth. This condition affects each individual in a different way, with some having only motor control problems and others having cognitive impairment as well. It is important to realise that many patients with cerebral palsy are of normal intelligence. They have a problem with control of movement, often exacerbated by limb spasticity. In others there are writhing (athetotic) motions of the limbs at rest, which often become worse if the patient is sedated or concentrating on remaining still.
Parkinson’s Disease
This is a widespread degenerative movement disorder characterised by a difficulty in initiating movement and a marked limb tremor at rest. In many patients this tremor reduces significantly when purposeful movements are made. Patients often have difficulty in initiating movements, moving through doorways and in starting to speak. This leaves what seems like an ‘awkward pause’ before they reply to questions, but the patient should be given the necessary time to respond. Head and neck involvement can cause purposeless mandibular movements at rest. These usually disappear when the patient holds their mouth open for treatment. Many patients are unaware of their movements at rest. Initially the symptoms can be well controlled with dopaminergic agonists and monoamine oxidase inhibitor drugs, but this control is gradually lost as the disease progresses. These drugs reduce salivary flow, and most patients complain about a dry mouth.
Other degenerative movement disorders, such as those related to drug treatments (tardive diskinesias) or alcohol abuse, do not improve with medical treatment and pose an increasing challenge to/>
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