West syndrome is a severe form of epilepsy most common in infancy. It is characterized by infantile spasms, hypsarrhythmia and mental deficiency. With this said, diagnosis of West syndrome can still be made should 1 of the 3 symptoms be absent.
The infantile spasms that result are one of three types:
- Flexor spasms resemble a brief, self-hugging motion and involve flexion of the neck, trunk and limbs.
- Extensor spasms involve extension of the neck, trunk, and limbs.
- Mixed flexor-extensor spasms are the most common type and involve combinations of neck, trunk, and limb flexion and extension.
The most widely-used techniques to diagnose West syndrome include:
An EEG study uses electrodes placed on the scalp to record the patterns of electrical activity of the brain. The detection of hypsarrhythmia, especially during sleep, can indicate that a patient has infantile spasms. Hypsarrhythmia is a brain wave pattern seen when seizures are not occurring and is indicated by chaotic, high-voltage spikes on an EEG. This pattern is present in wakefulness but is enhanced during sleep. Therefore, an EEG study should ideally include recordings taken both during wakefulness and sleep to confirm a diagnosis of West syndrome.
In some cases, simultaneous video and EEG recording (“Video-EEG”) can be used to verify particular brain-wave patterns during infantile spasms and document the patterns between the spasms.
Approximately 70-80% of patients with West syndrome present with abnormal findings on neuroimaging studies; these aim to identify the underlying causes of West syndrome. It is important that neuroimaging is done before the start of specific therapies- particularly ACTH or steroid therapy- which are associated with the possible appearance of brain atrophy as therapy progresses.
A computed tomography (CT) scan uses X-rays to generate computerized images of cross-sections of the brain; the detail from these allows the development of the brain to be studied. On the other hand, Magnetic Resonance Imaging (MRI) scans produce detailed images of cross-sections or slices of the brain by using the magnetic properties of particular atoms present in the brain.
Both imaging techniques can be used to detect an underlying brain infection or structural abnormalities associated with the syndrome in children. Of the two, the MRI scan is much more sensitive and likely to discover an abnormality of the brain. In fact, an MRI scan can show many neurologic abnormalities (such as developmental brain abnormalities) and evidence of brain injury incidents (such as those resulting from trauma, lack of oxygen, or from infection).
These may be necessary to determine if there is a metabolic or genetic disease responsible for a case of West syndrome. In fact, more than 50 genetic or metabolic diseases have already been associated with the syndrome. A blood, urine or cerebrospinal sample may be taken if family history or examination indicates the possibility of a metabolic or genetic disorder. For example, a diagnosis of nonketotic hyperglycemia requires a lumbar puncture to test for glycine.
Molecular genetic testing is also available and is already used to test for tuberous sclerosis complex (associated with symptomatic West syndrome) and mutations in genes ARX and CDKL5 (associated with X-linked West syndrome).
It is not uncommon for diagnosis of West syndrome to be delayed and this may occur due to many reasons:
- The EEG study does not show hypsarrythmia
- The child is considered too old to likely suffer from the disorder
- The spasms appear atypical; they may change between different seizure types or may occur singly rather than in the characteristic cluster.