Neurological disorders

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Neurological disorders

The central nervous system comprises 100 000 million neurones and when it malfunctions it has the potential to generate a wide spectrum of clinical problems. The site of the dysfunctional neurones determines the nature of the problem, which may involve impaired movement, vision, hearing, sensory perception, memory or consciousness. Classifying this wide range of symptom complexes can be problematic.

Headache

Headache is a frequent reason for older children and adolescents to consult a doctor. The International Headache Society (IHS) has devised a classification, as shown in Box 27.1, which defines:

Box 27.1   The classification of headache disorders

Primary headaches

Tension-type headache

This is a symmetrical headache of gradual onset, often described as tightness, a band or pressure. There are usually no other symptoms.

Migraine with aura

Accounts for 10% of migraine. The headache is preceded by an aura (visual, sensory or motor), although the aura may occur without a headache. Features are the absence of problems between episodes and the frequent presence of premonitory symptoms (tiredness, difficulty concentrating, autonomic features, etc.).

The most common aura comprises visual disturbance, which may include:

Rarely, there are unilateral sensory or motor symptoms.

Episodes usually last for a few hours, during which time children often prefer to lie down in a quiet, dark place. Sleep often relieves the bout.

Symptoms of tension-type headache or a migraine often overlap. They are probably part of the same pathophysiological continuum, with evidence that both result from primary neuronal dysfunction, including channelopathies, with vascular phenomena as secondary events. There is a genetic predisposition, with first- and second-degree relatives often also affected. Bouts are often triggered by a disturbance of inherent biorhythms, such as late nights or early rises, stress, or winding down after stress at home or school. Certain foods, e.g. cheese, chocolate and caffeine, are only rarely a reliable trigger. In girls, headaches can be related to menstruation and the oral contraceptive pill.

Uncommon forms of migraine

These include:

• Familial – linked to a calcium channel defect, dominantly inherited

• Sporadic hemiplegic migraine

• Basilar-type migraine – vomiting with nystagmus and/or cerebellar signs

• Periodic syndromes – often precursors of migraine and include:

Secondary headaches

Raised intracranial pressure and space-occupying lesions

Headaches often raise the fear of brain tumours; it may well be the reason for parents to consult a doctor. Headaches due to a space-occupying lesion are worse when lying down and morning vomiting is characteristic. The headaches may also cause night-time waking. There is often a change in mood, personality or educational performance. Other features suggestive of a space-occupying lesion are:

• Visual field defects – from lesions pressing on the optic pathways, e.g. craniopharyngioma (a pituitary tumour)

• Cranial nerve abnormalities causing diplopia, new-onset squint or facial nerve palsy. The VIth (abducens) cranial nerve has a long intracranial course and is often affected when there is raised pressure, resulting in a squint with diplopia and inability to abduct the eye beyond the midline. It is a false localising sign. Other nerves are affected depending on the site of lesion, e.g. pontine lesions may affect the VIIth (facial) cranial nerve and cause a facial nerve palsy

• Abnormal gait

• Torticollis (tilting of the head)

• Growth failure, e.g. craniopharyngioma or hypothalamic lesion

• Papilloedema – a late feature

• Cranial bruits – may be heard in arteriovenous malformations but these lesions are rare.

Management

The mainstay of management is a thorough history and examination with detailed explanation and advice. Imaging is unnecessary in the absence of any Red Flag features.

Children and parents should be informed that recurrent headaches are common. For most there are good and bad spells, with periods of months or even years in between the bad spells, and that they cause no long-term harm. Written child-friendly information for the family to take home is helpful. Children should be advised on how to live with and control the headaches, rather than allowing the headaches to dominate their lives. There is nothing medicine can do to cure this problem but there is much it can offer to make the bad spells more bearable.

Seizures

A seizure is a clinical event in which there is a sudden disturbance of neurological function caused by an abnormal or excessive neuronal discharge. Seizures may be epileptic or non-epileptic.

The causes of seizures are listed in Box 27.2.

Box 27.2   Causes of seizures

Febrile seizures

A febrile seizure is a seizure accompanied by a fever in the absence of intracranial infection due to bacterial meningitis or viral encephalitis. These occur in 3% of children, between the ages of 6 months and 5 years. There is a genetic predisposition, with a 10% risk if the child has a first-degree relative with febrile seizures. The seizure usually occurs early in a viral infection when the temperature is rising rapidly. The seizures are usually brief, and are generalised tonic-clonic seizures. About 30–40% will have further febrile seizures. This is more likely the younger the child, the shorter the duration of illness before the seizure, the lower the temperature at the time of seizure and if there is a positive family history.

Simple febrile seizures do not cause brain damage; the child’s subsequent intellectual performance is the same as in children who do not experience a febrile seizure. There is a 1–2% chance of developing epilepsy, similar to the risk for all children.

However, complex febrile seizures; i.e. those which are focal, prolonged, or repeated in the same illness, have an increased risk of 4–12% of subsequent epilepsy.

The acute management of seizures is described in Chapter 6. Examination should focus on the cause of the fever, which is usually a viral illness, but a bacterial infection including meningitis should always be considered. The classical features of meningitis such as neck stiffness and photophobia may not be as apparent in children <18 months of age, so an infection screen (including blood cultures, urine culture and lumbar puncture for CSF) may be necessary. If the child is unconscious or has cardiovascular instability, lumbar puncture is contraindicated and antibiotics should be started immediately.

Parents need reassurance and information. Advice sheets are usually given to parents. Antipyretics have not been shown to prevent febrile seizures and tepid sponging is no longer recommended. The family should be taught the first aid management of seizures. If there is a history of prolonged seizures (>5 min), rescue therapy with rectal diazepam or buccal midazolam can be supplied. Oral prophylactic anti-epileptic drugs are not used as they do not reduce the recurrence rate of seizures or the risk of epilepsy. An EEG is not indicated as it does not serve as a guide for treatment; nor does it predict seizure recurrence.

Summary

Febrile seizures

Paroxysmal disorders

There is a broad differential diagnosis for children with paroxysmal disorders (‘funny turns’). Epilepsy is a clinical diagnosis based on the history from eyewitnesses and the child’s own account. If available, videos of the seizures or suspected seizures can be of great help. The diagnostic question is whether the paroxysmal events are that of an epilepsy of childhood or one of the many conditions which mimic it (Fig. 27.1). The most common pitfall is that of syncope leading to an anoxic (non-epileptic) tonic-clonic seizure.

image
Figure 27.1 Causes of ‘funny turns’.

The key to the diagnosis lies in a detailed history, which, together with clinical examination, will determine the need for an EEG or other investigations.

Summary

Breath-holding and reflex anoxic seizures

In toddlers:

Epilepsies of childhood

Epilepsy has an incidence of about 0.05% (after the first year of life when it is even more common) and a prevalence of 0.5%. This means that most large secondary schools will have about six children with an epilepsy. Epilepsy is a chronic neurological disorder characterised by recurrent unprovoked seizures, consisting of transient signs and/or symptoms associated with abnormal, excessive or synchronous neuronal activity in the brain. Most epilepsy is idiopathic but other causes of seizures are listed in Box 27.2.

An international classification of epilepsy is used, which has recently been revised (International League Against Epilepsy (ILAE) 2010 Classifications). This broadly classifies seizures as either:

Focal seizure manifestations will depend on the part of the brain where the discharge originates:

• Frontal seizures – involve the motor or premotor cortex. May lead to clonic movements, which may travel proximally (Jacksonian march). Asymmetrical tonic seizures can be seen, which may be bizarre and hyperkinetic and can be mistakenly dismissed as non-epileptic events. Atonic seizures may arise from mesial frontal discharge.

• Temporal lobe seizures, the most common of all the epilepsies – may result in strange warning feelings or aura with smell and taste abnormalities and distortions of sound and shape. Lip-smacking, plucking at one’s clothing and walking in a non-purposeful manner (automatisms) may be seen, following spread to the pre-motor cortex. Déjà-vu and jamais-vu are described (intense feelings of having been, or never having been, in the same situation before). Consciousness can be impaired and the length of event is longer than a typical absence.

• Occipital seizures – cause distortion of vision.

• Parietal lobe seizures – cause contralateral dysaesthesias (altered sensation), or distorted body image.

In focal seizures, the level of consciousness may be retained, consciousness may be lost, or the seizure may be followed by generalised tonic-clonic seizure. In the new classification, the terms, simple or complex or discognitive are no longer used and the impairment of consciousness is not classified but described.

In many children, especially under 5 years old, it may be unclear whether a seizure is generalised or focal.

The main seizure types are summarised in Figure 27.2 and the epilepsy syndromes in Table 27.1.

Table 27.1

Some epilepsy syndromes – arranged by age of onset

Name Age Seizure pattern Comments
West syndrome 4–6 months Violent flexor spasms of the head, trunk and limbs followed by extension of the arms (so-called ‘salaam spasms’). Flexor spasms last 1–2 s, often multiple bursts of 20–30 spasms, often on waking, but may occur many times a day.
May be misinterpreted as colic. Social interaction often deteriorates – a useful marker in the history		 Many causes; two-thirds have underlying neurological cause. The EEG shows hypsarrhythmia, a chaotic pattern of high-voltage slow waves, and multi-focal sharp wave discharges (Fig. 27.3). Treatment is with vigabatrin or corticosteroids; good response in 30–40%, but unwanted effects are common.
Most will subsequently lose skills and develop learning disability or epilepsy
Lennox–Gastaut syndrome 1–3 years Multiple seizure types, but mostly drop attacks (astatic seizures), tonic seizures and atypical absences. Also neurodevelopmental arrest or regression and behaviour disorder Often other complex neurological problems or history of infantile spasms.
Prognosis is poor
Childhood absence epilepsy 4–12 years Stare momentarily and stop moving, may twitch their eyelids or a hand minimally. Lasts only a few seconds and certainly not longer than 30 s. Child has no recall except realises they have missed something and may look puzzled or say ‘pardon’ on regaining consciousness.
Developmentally normal but can interfere with schooling.
Accounts for only 2% of childhood epilepsy		 Two-thirds are female.
The episodes can be induced by hyperventilation, the child being asked to blow on a piece of paper or windmill for 2–3 min, a useful test in the outpatient clinic. The EEG shows generalised 3/second spike and wave discharge, which is bilaterally synchronous during and sometimes between episodes (Fig. 27.4). Prognosis is good, with 95% remission in adolescence; 5–10% may develop tonic-clonic seizures in adult life
Benign* epilepsy, with centrotemporal spikes (BECTS) 4–10 years Tonic-clonic seizures in sleep, or simple focal seizures with awareness of abnormal feelings in the tongue and distortion of the face (supplied by the Rolandic area of the brain) Comprises 15% of all childhood epilepsies.
EEG shows focal sharp waves from the Rolandic or centrotemporal area. Important to recognise as it is benign and does not always require treatment. Almost all remit in adolescence
Early-onset benign* childhood occipital epilepsy (Panayiotopoulos type) 1–14 years Younger children – periods of unresponsiveness, eye deviation, vomiting and autonomic features. Older children – headache and visual disturbance including distortion of images and hallucinations Uncommon.
EEG shows occipital discharges. Remit in childhood
Juvenile myoclonic epilepsy Adolescence-adulthood Myoclonic seizures, but generalised tonic-clonic seizures and absences may occur, mostly shortly after waking. A typical history is throwing drinks or cornflakes about in the morning as myoclonus occurs at this time. Learning is unimpaired Characteristic EEG.
Response to treatment is usually good but lifelong.
A genetic linkage has been identified.
Remission unlikely

image

*Although called benign, may be specific learning difficulties in some children.

image
Figure 27.2 Epilepsy seizure types.
image
Figure 27.3 EEG of hypsarrhythmia in West syndrome. There is a chaotic background of slow-wave activity with sharp multi-focal components.
image
Figure 27.4 EEG in a typical absence seizure in childhood absence epilepsy. There is three per second spike and wave discharge which is bilaterally synchronous during, and sometimes between, attacks.

Investigation of seizures

EEG

An EEG is indicated whenever epilepsy is suspected. It is interpreted to identify a background that is abnormal for the child’s age; asymmetry or slowing that might suggest underlying structural abnormalities; or evidence of neuronal hyperexcitability such as sharp waves or spike-wave complexes. Many children with epilepsy have a normal initial EEG; and many children who will never have epilepsy have EEG abnormalities. Unless a seizure is actually captured, an EEG does no more than add supportive evidence (or not) for the diagnosis. If the standard EEG is normal, a sleep or sleep-deprived record can be helpful. Additional techniques are 24–h ambulatory EEG or, ideally, video-telemetry. For assessment prior to surgery, more invasive techniques such as subdural electrodes can be used.

Imaging

• Structural. MRI and CT brain scans are not required routinely for childhood generalised epilepsies. They are indicated if there are neurological signs between seizures, or if seizures are focal, in order to identify a tumour, vascular lesion, or area of sclerosis which could be treatable. MRI FLAIR (fluid-attenuated inversion recovery) sequences better detect mesial temporal sclerosis in temporal lobe epilepsy.

• Functional scans. While it is not always possible to see structural lesions, techniques have advanced to allow functional imaging to detect areas of abnormal metabolism suggestive of seizure foci. These include PET (positron emission tomography) and SPECT (single positron emission computed tomography), which use isotopes and ligands, injected and taken up by metabolically active cells. Both can be used between seizures to detect areas of hypometabolism in epileptogenic lesions. SPECT can also be used to capture seizures and areas of hypermetabolism. Functional MRI can be used alongside psychological testing –including memory assessment – to minimise the risk of postoperative impairment.

Management

Management begins with explanation and advice to help adjustment to the condition. A specialist epilepsy nurse may assist families by providing education and continuing advice on lifestyle issues. The decision whether to treat or not is related to the level of inconvenience seizures are bringing into the young person’s life. It is common practice not to institute treatment after a single unprovoked seizure.

Anti-epileptic drug (AED) therapy

Principles governing use are:

• Not all seizures require AED therapy. This decision should be based on the seizure type, frequency and the social and educational consequences of the seizures set against the possibility of unwanted effects of the drugs.

• Choose the appropriate drug for the seizure. Inappropriate AEDs may be detrimental, e.g. carbamazepine can make absence and myoclonic seizures worse.

• Monotherapy at the minimum dosage is the desired goal, although in practice more then one drug may be required.

• All AEDs have potential unwanted effects and these should be discussed with the child and parent.

• Drug levels are not measured routinely, but may be useful to check for adherence to advice or with some drugs with erratic pharmacokinetics, e.g. phenytoin.

• Children with prolonged seizures are given rescue therapy to keep with them. This is usually a benzodiazepine, e.g. rectal diazepam or buccal midazolam.

• AED therapy can usually be discontinued after 2 years free of seizures.

Guidance regarding treatment options for different seizure types are shown in Table 27.2. Common unwanted effects of AEDs are shown in Table 27.3.

Table 27.2

Choice of anti-epileptic drugs (NICE 2004)

Seizure type First-line Second-line
Generalised seizures    
 Tonic-clonic Valproate, carbamazepine Lamotrigine, topiramate
 Absence Valproate, ethosuximide Lamotrigine
 Myoclonic Valproate Lamotrigine
Focal seizures Carbamazepine, valproate
Lamotrigine shown since to be most effective – but slow titration		 Topiramate, levetiracetam, oxcarbazepine, gabapentin, tiagabine, vigabatrin

Table 27.3

Common or important unwanted effects of anti-epileptic drugs

Drug Side-effects
Valproate Weight gain, hair loss
Rare idiosyncratic liver failure
Carbamazepine/oxcarbazepine Rash, neutropenia, hyponatraemia, ataxia
Liver enzyme induction, can interfere with other medication
Vigabatrin Restriction of visual fields, which has limited its use
Sedation
Lamotrigine Rash
Ethosuximide Nausea and vomiting
Topiramate Drowsiness, withdrawal and weight loss
Gabapentin Insomnia
Levetiracetam Sedation – rare
Benzodiazepines – clobazam, clonazepam, diazepam, nitrazepam Sedation, tolerance to effect, increased secretions
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