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Chapter 7: Clinical 293

Foot-drop: This is caused by weakness of ankle dor- Characteristic abnormalities are described under

siflexion, usually a feature of a lower motor neurone Epilepsy, but include spikes and spike and wave dis-
disease such as a peripheral neuropathy. The knee is charges.
lifted high and as the ankle cannot dorsiflex, the foot Photic stimulation and hyperventilation are routinely
tends to slap on the ground. If bilateral, it is called a performed to increase the sensitivity if the resting EEG
high-stepping gait. is normal.
Ataxic: This is the typical gait of a person with cerebel- Sleep-deprived EEG, which allows recordings when

lar disease. The gait is broad-based, and there may be the patient dozes and wakes.
atendency to veer to the side of the lesion in unilateral EEGrecordinginstatusepilepticusisusefulatdemon-
disease. Even if mildly affected the patient is unable to strating whether seizure activity is suppressed by
walk heel-toe in a straight line. medication, particularly in a paralysed, ventilated
Parkinsonian: There is hesitancy, that is slowness in patient.

initiating movement, and turning. The steps are small TheEEGisabnormalpost-ictally,whichcanbehelpful
and shuffling, and the patient tends to be flexed or in the diagnosis of epilepsy.
stooped. ‘Festination’ is the hurrying steps which Focalabnormalities,e.g.localisingabnormalelectrical
appear to be the only way the patient can remain activity to the frontal lobe can suggest an underlying
upright. In the upper limbs, there is reduced arm epileptogenic focus, e.g. a tumour or area of infarction
swing, and increased tremor may be apparent. In or encephalitis, as well as occurring in focal status
Parkinson’s disease, this pattern tends to be asym- epilepticus.
metrical, whereas it is symmetrical in other causes of Encephalitis, cortical necrosis (e.g. in stroke or post-
parkinsonism. anoxic damage), metabolic brain disorders including
Waddling gait: Proximal muscle weakness such as oc- drug-induced delirium, and tumours can cause either

curs in myopathies leads to difficulty in rising to an focal or generalised EEG abnormalities. EEG changes
erect position and then the pelvis tends to drop on the are seen even before MRI changes are evident.
side of the lifted leg.
Antalgic gait: Pain around the joints or within the

muscles may give rise to abnormalities in gait (the Electromyography (EMG) and nerve
classical limp). conduction studies (NCS)
These are tests of the function of muscles (EMG) and
Investigations and procedures the peripheral nerves (NCS). They are useful in the di-
agnosis of muscle disease, diseases of the neuromuscular
Electroencephalography junction, peripheral neuropathies and anterior horn cell
disease.
An electroencephalogram (EEG) is a recording of the
electrical activity of the brain. It is obtained by placing
electrodes on the scalp, using a jelly to reduce electrical Electromyography
resistance. A recording of at least half an hour is usually Aneedleelectrodeisplacedintomusclesandinsertional,
needed, to maximise the chances of picking up tran- resting and voluntary electrical activity is studied, using
sient abnormalities. The patient needs to lie still, as elec- acomputer screen and a speaker.
trical changes due to movement can interfere with the Denervated muscle shows prolonged insertional ac-
recording. tivity, fibrillation potentials and positive sharp waves.
Its main use is for the classification of epilepsy, but is Peripheral neuropathies and anterior horn cell disease
it may also be useful in the diagnosis of other brain dis- lead to a reduced number of motor units, which fire
orders such as encephalitis. In epilepsy, different wave- rapidly.
forms may be seen. The EEG is often normal between Anterior horn cell disease – large motor units form,
seizures, and anti-convulsant medication can alter the causingvisiblefasciculations,whichcanalsobeshown
EEG. by EMG.