Available Investigations and Clinical Indications

Neurophysiology covers a wide range of procedures and this page seeks to explain to the clinician the indications and limitations of those currently available.

As at Sep-2015, the previously available wide range of Evoked Potentials are no longer available due to equipment redundancy. For a small external service provider such as us, the replacement costs vastly exceed the income from the very minimal referral numbers. The EEG service is however, very secure and we have just bought a new Video EEG system which will have 10+ years of working life.

vEEG - Routine Video ElectroEncephaloGraphy

A routine VEEG normally takes about 1 hour of which 20 minutes is setting up, 20 minutes is recording and 20 minutes is cleaning up. Reports are written after the event and are usually sent to the referring physician within two hours of the appointment.

The more specific your question on the request form, the more specific will be the report.

vEEG has a broad range of indications including:

• documentation of seizure by type, frequency, and severity

• documentation of sub-clinical seizures

• differentiating between common paediatric 'blank' or 'daydreaming' episodes and true absence seizures

• differential diagnosis of seizure vs. syncope

• differential diagnosis of seizure vs. pseudo-seizure

• differential diagnosis of seizure vs. behaviour manifestations

• other unexplained alterations in conciousness

• diagnosis and evaluation of sudden-onset dementias such as CJD

• exclusion of seizure components in psychiatric disorders

• evaluation of sleep disorders

• evaluation of efficacy of anticonvulsant therapy over the long term

• pre-screening prior to removal from anticonvulsants

A vEEG  can be of considerable use where an unexplained alteration in awareness has been reported. Where a formal diagnosis is yet to be made, a vEEG within 24 hours of such an 'event'  may show post-ictal changes and/or seizure activity and provide some diagnostic direction.

If an 'event' is electrocephalic in origin, a post-ictal disturbance will likely be recorded and so the EEG can be particularly useful to filter out non-cephalic (eg: vasovagal or supratentorial etc) causes.  Please note that if an on-demand vEEG is required for this purpose, we may be able to oblige at very short notice - please contact us.

SSLvEEG - Sleep-deprived Video ElectroEncephaloGraphy

Sleep deprivation is a useful additional tool and can be most helpful where an initial recording has shown no abnormalities. 

The procedure may also be of value in patients who report nocturnal seizures.

Where an event such as a LOC has occurred whilst driving and a Routine vEEG has been normal, then a Sleep-deprived vEEG may produce changes. However, the eligibility to drive is a function of the time since the last seizure and not the EEG findings which are intended to plan treatment.