Dr Millie Nakatsuka | Decoding Dizziness in the Emergency Room

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 if well-trained emergency physicians can differentiate between the two causes using a quick bedside physical examination without expensive special equipment.

Acute Vestibular Syndrome

Acute vestibular syndrome (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 (i.e., related to the brain) or peripheral (i.e., related to the inner ear). Knowing the location of the damage helps doctors identify which patients may be suffering from a potentially life or brain-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 8^th cranial nerve, which is not lethal (e.g., mild viral infection).

Central and Peripheral Causes

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 (VOG).

Doctors and healthcare workers can perform a HINTS examination to differentiate between central and peripheral AVS. The HINTS examination consists of three components: Head Impulse, Nystagmus, and 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 if 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 STANDING algorithm (SponTAnous or positional, Nystagus Direction, Head Impulse test, StaNdinG).

VOG 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.

Problems with Differentiation

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 specialised doctors such as neuro-ophthalmologists or neuro-otologists (specialists 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 in identifying stroke). The findings of these studies are particularly concerning when we think about the care of patients attending rural or remote hospitals that may not have access to doctors in every speciality or VOG technology.

Dr Millie Nakatsuka of the University of Sydney in Australia has a special interest in neuro-ophthalmology and a particular interest in health inequality in regional and rural hospitals. Working with a multidisciplinary team, Dr Nakatsuka conducted a large-scale review of published studies to evaluate whether appropriate training and education can allow emergency doctors to use the HINTS examination (or the latter variant) and, thus, 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 (descriptive and interpretative) analysis and two for quantitative (numerical) 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. The STANDING algorithm offers high levels of sensitivity – meaning that 96% of cases of central AVS were accurately detected, and also high levels of specificity – meaning that 88% of non-central AVS cases were ruled out, when administered by trained emergency doctors. 

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.

Implications for Diagnosis in Resource-limited Settings

Dr Nakatsuka’s study is the first provision of high-quality evidence supporting the diagnostic accuracy of the STANDING algorithm when conducted by trained point-of-care 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 VOG. The results of Dr Nakatsuka’s work are particularly important for less well-equipped hospitals as they highlight 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 having to travel to a large well-resourced city hospital (which is not practical or feasible).

Increasing interest in using 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.