Acute vestibular syndrome is one of the most common reasons people present at hospital with dizziness. The symptoms can arise from damage within the brain or the ear, and specialist medical knowledge or equipment is typically needed to determine the specific cause. Dr Nakatsuka from the University of Sydney in Australia has conducted a large-scale analysis and review of the published literature to determine whether well-trained emergency physicians can differentiate between the two causes, using a quick bedside physical examination without expensive special equipment. More
Acute vestibular syndrome – or AVS for short – is the onset of sudden and intense feelings of spinning or dizziness, often accompanied by nausea, balance problems, and involuntary eye movements known as nystagmus.
These symptoms can all be caused by damage or disease in the vestibular system – the network responsible for maintaining our sense of balance and spatial awareness. AVS can either be central, which is related to the brain, or peripheral, which is related to the inner ear. Knowing the location of the damage helps doctors identify which patients may be suffering from a potentially life-threatening medical condition. This is because central AVS is associated with severe morbidity. In contrast, peripheral AVS is a common condition of the inner ear or eighth cranial nerve, which is not lethal.
Diagnosing AVS and categorising the cause as either central or peripheral can be achieved by gathering a medical history, conducting physical and neurological examinations, and using complex diagnostic technology such as video oculography.
Doctors and healthcare workers can perform a HINTS examination to differentiate between central and peripheral AVS. The HINTS examination consists of three components: a head impulse test, a nystagmus test, and a test of skew.
The head impulse test involves rapid horizontal movements of the patient’s head while the patient focuses on a fixed point. Nystagmus are involuntary eye movements. Factors such as the presence or absence and direction of these movements can indicate whether AVS is central or peripheral. The test of skew analyses the alignment of the eyes. In central AVS, imbalances in the eye muscles can lead to one eye appearing higher than the other.
The original HINTS examination was established in 2009. Since then, variations have been released, including the HINTS-PLUS, which includes a hearing test, and the so-called STANDING algorithm.
Video oculography uses video goggles or a specialised camera to track a patient’s eye movements. It is highly accurate and may capture subtle abnormalities that would be missed by a physical examination. It is also a highly specialised piece of equipment requiring trained healthcare staff to perform the tests and interpret the results.
A recent review paper found that less than 20% of patients who came to hospital with severe dizziness underwent a HINTS examination. Several studies have suggested that only doctors specialising in eye or ear problems relating to the nervous system are able to correctly conduct and interpret physical and neurological examinations such as the HINTS examination, which is better than an early MRI for identifying stroke. The findings of these studies are particularly concerning when we think about the care of patients attending rural or remote hospitals, who may not have access to specialist doctors or video-oculography technology.
Dr Millie Nakatsuka of the University of Sydney in Australia is an expert in neuro-ophthalmology and has a particular interest in health inequality in regional and rural hospitals. Working with a multidisciplinary team, Dr Nakatsuka conducted a large-scale review to evaluate whether appropriate training and education can allow emergency doctors to use the HINTS examination and STANDING algorithm to effectively distinguish between central and peripheral AVS.
The team began by looking at 1,757 results from all the major clinical journals and clinical trial records. Of these, 27 were deemed appropriate for further consideration. Articles were screened against multiple factors to ensure they met the stated criteria for clinician education and did not contain significant bias. After being screened, five studies were available for qualitative analysis and two for quantitative analysis.
More information was available on the STANDING algorithm than the traditional HINTS examination and its variations. Data supported the proposal that emergency doctors who are well-trained and educated can use the STANDING algorithm to identify central AVS in comparison to AVS with a peripheral cause. When administered by trained emergency doctors, the STANDING algorithm offered high levels of sensitivity, as 96% of cases of central AVS were accurately detected. It also showed high specificity, as 88% of non-central AVS cases were ruled out.
The researchers did not find enough evidence to fully support emergency doctors’ use of the original HINTS examination. However, they did report that two separate research studies are currently being conducted to assess the reliability of HINTS when performed by trained emergency doctors.
Dr Nakatsuka’s study provides the first high-quality evidence supporting the diagnostic accuracy of the STANDING algorithm when conducted by trained emergency doctors. As such, the team’s findings contradict previous reports concluding that bedside physical examinations for AVS should only be conducted by specialist doctors.
In Australia, only 25% of public hospitals are in major cities, with rural and regional hospitals facing large disparities in access to medical specialities and diagnostic technology such as video-oculography. Dr Nakatsuka’s work shows that if staff are given adequate education and training, patients will be able to be rapidly and accurately classified as having central or peripheral AVS without needing to travel to a large well-resourced city hospital.
Increasing interest in the use of smartphones to record eye movements to aid AVS diagnosis also emerged in Dr Nakatsuka’s work, illustrating the useful application of technology and clinical skills. She hopes to build upon this current work by conducting further research on the education and training needed by point-of-care healthcare professionals to provide robust AVS differential diagnoses.