Nystagmus

A 65 year old man presents to the emergency department with a sudden onset of ‘dizziness’. He feels more dizzy on any head movement as well as on sitting up. He is finding it difficult to walk around as his balance is affected.

This is a common presentation in emergency departments and our main role here is the determination of whether this is a peripheral or central cause. We know that in some cases central causes can be difficult to differentiate from peripheral. In this month’s ‘Medical Talk’, we go into ‘vertigo and nystagmus’ and discuss the means of determining the difference. We look at methods that have been in place for some time and then consider new advances.

A very common complaint of patients such as this one, presenting to the emergency department, is ‘dizziness’. In most cases the patient is referring to vertigo but we must clarify this. Vertigo is the perception of movement where there is none. The patient may move in respect to their surroundings or vice versa. The important thing to distinguish is whether or not this is a central or peripheral cause; this is where the challenge lies.

Vertigo is caused by a non-integration or non-correlation of inputs from our senses responsible for our spatial positioning. The sensory organs involved are:

1 vision- which determines our spatial orientation

2 proprioception – which determines body position

3 vestibular system – which determines our position in relation to gravity

Inputs from these areas determine outputs that drive the vestibulo-occular reflex (VOR).

Nystagmus which is a clinical finding in most cases is of significant assistance in respect to making the diagnosis. Nystagmus is a rhythmical  movement of the eyes and has a fast and slow component. The side of the nystagmus is named after the fast component of the movement. The slow component is the result of the VOR. When speaking of determining a central or peripheral cause, we are referring to horizontal nystagmus. Vertical nystagmus is always to be considered serious and in most cases is of brainstem aetiology.

Let’s speak a little about the VOR. If you turn the head to the right quickly, the VOR is responsible for moving your eyes back to the centre. This has benefits in terms of maintaining focus on objects. The old discussion of ‘doll’s eye’ movement in brainstem death is related to patients that have lost the ability to move eyes back to centre. They are the dolls of old days where the eyes were painted on, so when the head is moved the eyes move with it – this is brainstem aetiology. So when the neurosurgeons come to your emergency department and turn the patient’s head from side to side and look at what the eyes are doing, this is what they are looking for.

This month in ‘Medical Talk’, we demonstrate a very helpful sign, the ‘head thrust’ test, which evokes the VOR. We look at dividing the causes of vertigo into a more clinical orientated rather than the time-old listing of potential causes. To all the guys that subscribe, enjoy the issue. It is posted out on Monday the 6th. We also cover our favourite (sarcasm) topic; atrial fibrillation in detail, detail, detail. Enjoy. For those that don’t get ‘Medical Talk’, join the club at $178 AUD for a year’s membership, it is probably the most value for money, emergency medicine investment, you will ever make.