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(BQ) Part 2 book Textbook of clinical neurology has contents: Cerebral infarction and cerebral haemorrhage, epilepsy and other paroxysmal disorder, altered consciousness, neurological tumours and neurological complications of malignant conditions,... and other contents.
195 Disorders of the cranial nerves Abstract Diseases of the cranial nerves result in sensory function loss and/or the loss of facial motor control Hearing and sight may be lost, for example, double vision or vertigo may occur, swallowing and speech may become difficult, and the face may become paralysed or hypersensitive Cranial nerve problems can usually be traced and resolved That is the case, for example, with viral infections, compression due to intracranial hypertension, drug poisoning, autoimmune disorders and meningitis 16.1 General causes – 196 16.2 Clinical presentation – 196 16.2.1 Olfactory nerve (I) – 196 16.2.2 Optic nerve (II) – 197 16.2.3 Oculomotor nerve (III) – 198 16.2.4 Trochlear nerve (IV) – 200 16.2.5 Trigeminal nerve (V) – 200 16.2.6 Abducens nerve (VI) – 200 16.2.7 Facial nerve (VII) – 200 16.2.8 Vestibulocochlear nerve (VIII) – 202 16.2.9 Glossopharyngeal nerve (IX) and vagus nerve (X) – 204 16.2.10 Accessory nerve (XI) and hypoglossal nerve (XII) – 205 16.3 Failure of multiple cranial nerves – 205 lectronic supplementary material E The online version of this chapter (7 https://doi.org/10.1007/978-90-368-2142-1_16) contains supplementary material, which is available to authorized users © Bohn Stafleu van Loghum is een imprint van Springer Media B.V., onderdeel van Springer Nature 2018 J B M Kuks and J W Snoek (Eds.), Textbook of Clinical Neurology, https://doi.org/10.1007/978-90-368-2142-1_16 16 196 Chapter 16 · Disorders of the cranial nerves Case 16.1 A sixty-year-old man has sometimes been seeing double for the last three months When it happens, the images are displaced diagonally The double vision is present when the man wakes up in the morning, but after an hour or so it disappears, and for the rest of the morning he is fine However, the double vision usually returns in the course of the afternoon, especially if the man drives or has been reading a lot For the last week, the man’s right upper eyelid has been drooping, particularly in the evening However, when the eyelid droops, the man no longer has double vision He has no other symptoms During a morning examination, no abnormalities are initially observed However, when the man directs his gaze upward for about fifteen seconds, the double vision starts and his left eye is observed to be lower than his right When he directs his gaze to the right, he experiences uncrossed double vision and he cannot keep his right eye directed to the side; it gradually drifts back towards his nose The upper eyelid also droops to partially cover the pupil Question 1: Which muscles are affected? Question 2: What needs to be tested in order to establish whether the patient has an eye muscle disorder or a cranial nerve disorder? Question 3: What is the most likely diagnosis? Online: 7Answers to case study questions 16.1 Case 16.2 16 A fifty-five-year-old woman has experienced five acute vertigo attacks in the last year, each lasting several hours During the attacks, she has the sense that everything around her is spinning Sometimes she is also nauseous; indeed, during the last attack, she had to vomit According to her husband, her eye movements were jerky Prior to the attacks, she has often had the sensation that her right ear was blocked The attacks are also accompanied by tinnitus Onset appears unrelated to the woman’s posture or the time of day, and there is no apparent trigger Between attacks, the woman’s balance is good, but her hearing on the right remains affected When examined twenty-four hours after an attack, the hearing in her right ear is found to be impaired The result of Rinne’s test is abnormal and Weber’s test reveals lateralization to the left Question 1: What disorder does the patient probably have? Question 2: How should the results of the tuning fork tests be interpreted? Question 3: What did the patient’s jerky eye movements probably entail? Online: 7Answers to case study questions 16.2 16.1 General causes The twelve cranial nerves share the characteristic of running over the base of the skull to and from the associated sense organs or effectors With the exception of the first two, they all originate in the brainstem (7sect. 6.2) Their location makes them vulnerable to traumatic injury (especially nerves I, II, IV and VII) and to intracranial hypertension, whether or not accompanied by compression (nerves III and VI) Furthermore, all of them can be affected by basal meningitis (bacterial, granulomatous in sarcoidosis) and by leptomeningeal metastases Local compression can be caused by cranial base processes (chondroma, metastases) and nasopharyngeal tumours, meningiomas (mainly nerves II, V, VI, VII and X) and aneurysms (nerve III, sometimes nerve II) The tumours that originate in cranial nerves are olfactory meningioma (nerve I), optic glioma (nerve II) and neurinoma (mainly in nerve VIII, but also nerve V and occasionally nerves VII, X and XII) Almost all cranial nerves (except XI and XII) can be affected by herpes virus infection Some cranial nerves are involved in MS (nerves II, V, VI, sometimes nerve VII, occasionally nerves III, X and XII) Diabetes mellitus can affect nerves II, III and VI and sometimes nerves VII and X Collagen disease and vasculitis can affect nerves II, III, V, VI and sometimes nerve VII However, it is by no means always possible to identify a cause for the impairment of cranial nerve function The clinical examination undertaken in cases of cranial nerve disorder is described in 7sect. 6.3 This chapter discusses the clinical presentations of cranial nerve disorders 16.2 Clinical presentation 16.2.1 Olfactory nerve (I) The connections between the receptors in the olfactory mucous membrane and the olfactory bulb (7sect. 6.2) are vulnerable Consequently, the sense of smell may remain impaired after a relatively minor traumatic brain injury, e.g contrecoup phenomenon or fall-related impact injury to the occipital region (7sects. 20.3.2 and 20.6.5) Loss of smell is a common resi dual symptom of ‘influenza’ Finally, loss of smell is sometimes attributable to a frontal process, particularly olfactory meningioma Olfactory sensations can be triggered by partial epilepsy (uncinate fits; 7sect. 18.2.1), but may also originate from the nasal sinuses 197 16.2 · Clinical presentation Loss of smell Olfactory nerve dysfunction traumatic brain injury tumour in anterior cranial fossa (olfactory meningioma) 5 sarcoidosis status after meningitis Parkinson’s disease following ‘influenza’ or other viral infection congenital defect (atrophy of the olfactory bulb) Other causes acute or chronic nasal infection, heavy smoking 5 familial unknown cause 16.2.2 Optic nerve (II) Impaired visual acuity of one eye often requires ophthalmological investigation, but sometimes a neurologist is involved on a secondary basis A partial visual field disorder of both eyes is nearly always a matter for a neurologist The anatomy of the visual system and the associated examination and testing procedures are described in 7 chap. 9 In cases of neuropathy of the optic nerve, distinction is made between disorders characterized by observable abnormalities of the papilla and other disorders Disorders that not involve papillary abnormalities are referred to as posterior or retrobulbar disorders, or as retrobulbar neuritis; where such abnormalities are present, the disorder is known as anterior optic neuritis About 3 % of the population has a ‘lazy eye’ (amblyopia) with vision of between 1/10 and 1/60, without experiencing a specific visual field disorder and without any other ophthalmological or neurological abnormalities being detectable Causes of vision impairment Vascular ischemia of the retina ischemia of the optic nerve Infection of the optic nerve demyelinating optic neuritis (e.g in MS) viral infection (children) Optic neuropathy 5 toxic 5 metabolic hereditary (mitochondrial, SCA, 7sect. 25.3) Mechanical injury to optic nerve infiltration in basal meningitis infiltration in leptomeningeal metastasis 5 compression 5 trauma Primary eye disorders retinopathy, macular degeneration glaucoma and other primarily ophthalmological causes Other 5 amblyopia Vascular causes of impaired vision Distinction may be made between ischemia of the retina (amaurosis fugax, retinal infarct) and ischemia of the optic nerve papilla (anterior ischemic optic neuropathy, (AION) or posterior ischemic optic neuropathy (PION)) Ischemic optic neuropathy involves acute painless impairment to the vision of one eye, often followed by further deterioration in the following hours or days If abnormalities are visible in fundo, the disorder is referred to as AION, and otherwise as PION Consideration should always be given to temporal arteritis, but the cause may also be generalized vascular pathology Such optic ischemia is attributable to local occlusion of minor blood vessels and not to a thromboembolic disorder; hence, neither examination of the heart nor examination of the blood vessels of the neck is indicated It is a different matter in cases of ischemia of the retina The retina is supplied with blood by the central retinal artery, which branches off the ophthalmic artery, itself a branch of the internal carotid artery (.fig. 11.3) In a case of ischemia of the retina, whether temporary (amaurosis fugax) or permanent (retinal infarct), examination and testing should be the same as in a case of cerebral TIA or infarction (7 chap. 17) Migraine can sometimes cause temporary visual field impairment affecting one eye However, if migraine is the cause, the impairment is not sudden, but progresses gradually, often starting peripherally and migrating inward, and the impairment soon disappears (retinal migraine) The latter disorder mainly affects young adults It is not clear whether migraine-related visual field impairment is a vascular pheno menon (7sect. 21.1.3) Neuritis of the optic nerve Optic neuritis can occur in demyelinating disorders Usually, no abnormalities of the optic nerve are observable in the acute stage and the condition is referred to as retrobulbar neuritis; sometimes, however, oedema of the optic nerve papilla is immediately visible Within hours or a few days, an impairment will develop at the centre of the field of vision of one eye (central scotoma), resulting in visual acuity declining to between 1/10 and 1/60 The peripheries of the fields of vision remain largely unaffected The eye will also be painful, particularly when moved or subject to external pressure The impaired vision is often accompanied by impaired colour perception Examination should reveal an afferent pupil defect (7sect. 6.3.2) The prognosis is generally good; a gradual improvement starts after a week or so, and most patients regain normal vision after three to six weeks Relapse can occur, however, and the same disorder may develop in the other eye Generally 16 198 Chapter 16 · Disorders of the cranial nerves speaking, more than 50 % of patients with optical neuritis subsequently develop MS The extent to which one should anticipate that possibility by additionally testing for MS and the circumstances under which one should treat optic neuritis resulting from demyelination are matters of debate Neuropathy of the optic nerve Toxic neuropathy of the optic nerve can be caused by methanol, excessive nicotine, drugs such as chloroquine, quinine, streptomycin, chloramphenicol, lead, arsenic and certain insecticides A deficiency of vitamin B12 or vitamin B1 can lead to vision impairment Mitochondrial disorders Hereditary mitochondrial optic neuropathy (Leber’s hereditary optic neuropathy) usually develops gradually over the course of weeks or months and is characterized by central vision impairment affecting both eyes Sometimes, however, it starts with acute retrobulbar neuritis The disorder occurs mainly in men aged between eighteen and thirty-five, but it can also become manifest later in life and is occasionally found in women It is associated with various mutations in the mitochondrial DNA However, none of the mutations can fully explain the disorder’s manifestation, because the same DNA abnormalities can be found in family members with unimpaired vision The prognosis is relatively poor: although improvement sometimes occurs, significant permanent impairment (