The practice of medicine is a finely balanced art. Clinical features are often very subtle, and the ground is littered with booby traps. You could say medicine is a minefield, strewn with mimics and chameleons (apologies Practical Neurology). This explains why diagnostic error is rife in medicine, and this is perhaps more so in neurology. Admittedly, some misdiagnoses only cause minor emotional trauma to the patient…and some  embarrassment to the neurologist. Other missed diagnoses are however supremely consequential because they prevent early curative treatment, and result in death or severe disability. And every so often…a place in the dog house for the unwitting doctor.

To highlight the problem of neurological errors, I have compiled a list of 7 hazardous neurological misdiagnoses. To restrict myself to the iconic number 7, I have had to drop many perhaps equally serious diseases but these are conditions where the diagnosis, even though critical, is often obvious such as stroke. I have also excluded misdiagnoses which are critical but almost uniformly lead to death, for example malignant brain tumours and motor neurone disease (MND). Below therefore are my 7 deadly sins of neurological misdiagnosis.

 

Bacterial meningitis

This is inflammation of the meninges, the covering of the brain, and it typically manifests with neck stiffness, impaired consciousness, and in some cases, a skin rash. The examination may reveal such signs as those of Kernig and Brudzinski. All these may however be missing, or easily missed, in the early phases; this makes meningitis a pitfall both to the wary and the unwary. The commonest cause of bacterial meningitis is Streptococcus pneumoniae, but almost any organism can infect the meninges. The consequences of meningitis, from deafness to death, are not savoury. Unfortunately, when looked at retrospectively, it is always easy to conclude that a missed diagnosis of meningitis was negligent. Because of the catastrophic clinical, and legal, consequences of meningitis, some sages consider any doctor whose diagnosis of meningitis is wrong 9 out of 10 times to be a good doctor; so long as something equally deadly is not missed in the process, no case of meningitis, no matter how camouflaged, is likely to escape this doctor’s dragnet. You can checkout more on bacterial meningitis with the clinical features and management checklists. And whilst at it, you can also take look at a host of other neurological infections: viral, bacterial, parasitic, and fungal.

 

Subarachnoid haemorrhage (SAH)

The one word that captures this cataclysmic event is – cataclysmic. It strikes, like a bolt from the blue, with no warning whatsoever. It often presents with what has been aptly termed a thunderclap headache – famously depicted as being hit on the back of the head with a cricket bat (I guess it will be as painful if it was a baseball bat). It is most often the result of a cerebral aneurysm which has bursted and discharged its contents into the subarachnoid space that surrounds the brain. Whilst the subject may lose consciousness, many victims are walking wounded and the doctor may thereby underestimate the seriousness of the situation. The risk of missing the diagnosis is also heightened by the usual absence of focal neurological deficits – this is because the brain substance is usually not disrupted by the bleeding. The need to diagnose the bleed and the aneurysm is paramount to save life and prevent future bleeds, and missing this seminal event is often looked on very unfavourably by the men and women in white wigs. You can check out the following 13 subarachnoid haemorrhage checklists which cover everything from causes to coil embolisation. You may also review the 10 aneurysm checklists which cover topics such as risk factors and screening.

Giant cell arteritis (GCA)

Giant cell arteritis is indeed a giant problem for a variety of medical and surgical specialties – from ophthalmology and rheumatology to vascular surgery and of course neurology. Its monicker, temporal arteritis, does not do justice to the diversity of blood vessels it can affect. From headache to stroke, from blindness to aortic aneurysms, GCA wreaks havoc on whatever artery it invades. It causes inflammation of the vessel causing it to close off and starve the target tissue of blood supply. It is also a systemic disease causing such symptoms as fever, weight loss, intermittent jaw claudication, and polymyalgia rheumatica. It is therefore no wonder that GCA can readily evade even the astute physician, the only remedy being to always suspect it in anyone >50 years of age – whatever their symptoms. There are of course GCA checklists to help, and they cover pathology and diagnostic criteria, clinical features, investigations, and treatment.

Idiopathic intracranial hypertension (IIH)

For some unfathomable reason, this scourge mainly targets young females of a certain weight. The experts are still struggling to understand its interminable riddle. What we do now about IIH is that there is an increase in the pressure of the cerebrospinal fluid around the brain. This increased pressure can cause headaches and visual disturbances, and when the retina of the eye is examined with an ophthalmoscope, the optic nerve often appears swollen – a phenomenon called papilloedema (ignore the ‘o’ if you are from across the Atlantic). Whilst the headache is the most prominent feature of IIH, it is important to realise that headache is not always present. This emphasises the need for vigilance in making the diagnosis of IIH because the real consequence of misdiagnosis is the threat of visual field constriction and ultimate blindness. The failure to examine the back of the eye in anyone with a headache, let alone one who fits the typical phenotype of IIH, is one that has often opened the door to the dock. Perhaps these IIH clinical features checklists may help to shut that door: typical clinical features, unusual presentations, co-morbid disorders, variant types, IIH in children, medical differentials, and drug differentials. There are also 8 IIH management checklists covering all aspects of this fearsome neurological sin.

Cerebral vein thrombosis (CVT)

If you can imagine the nightmare a clot in a leg vein is, then you can imagine the torment a clot in a vein of the brain will be. Caused by a variety of haematological risk factors and non-haematological risk factors, a cerebral vein thrombosis may result in such serious clinical features as stroke and raised intracranial pressure. To put it crudely, CVT is easy to miss. A plain CT scan is usually normal, and the investigations require a venogram scan, D-dimer estimation, and a thrombophilia or clotting tendency screen. The main reatment is with blood thinning drugs – even if there is evidence of bleeding complicating the clot! Other treatments include anti-epileptic drugs, thrombectomy (clot removal), and treatment of raised intracranial pressure. With so many treatments, it is no surprise that missing the diagnosis of CVT comes with such a hefty penalty.

Encephalitis

Whilst meningitis is restricted to the meninges, encephalitis is infection of the brain substance itself. In practice the two may occur together, but encephalitis usually involves a slightly different set of players. Viruses, for example, often cause meningitis of little consequence, but in the brain, they leave a terrible trail of destruction. The major culprit in this regard is herpes simplex virus type 1 or HSV1, but it is by no means the only viral agent of encephalitis. HSV1, for no reason whatsoever, finds comfort in the temporal lobes of the brain where it causes seizures, impaired memory, and behavioural disturbances. When treatment is instituted early, HSV encephalitis is usually benign, but it may be complicated by relapse, post-herpes autoimmune encephalitis, and chronic herpes encephalitis. There are also several other forms of autoimmune encephalitis, all potential fatal to the patient. Because encephalitis is eminently treatable, it is understandable that the law tends to turns a deaf ear to any excuses for its misdiagnosis.

Cervical artery dissection (CAD)

Dissection describes the development of a tear in the wall of any artery; for the neurologist, the favoured vessels are the carotids and the vertebrals – the two large paired arteries in the neck. The tear results in a space within the vessel wall which may give rise to a clot which then dislodges and travels up to block a smaller artery, resulting in stroke. Alternatively, the space may become engorged with blood which expands and narrows the lumen of the affected artery, thereby starving the brain of blood and also resulting in a stroke. Cervical artery dissection is a wily disorder to diagnose because it doesn’t readily show its hand like most other strokes. For one, it often starts surreptitiously as neck pain; this may result from neck manipulation or extension, but there are several other risk factors. It is only much later that the headache, stroke and other clinical features of CAD develop – after the clot has had time to form, dislodge, and migrate. Furthermore, unlike other forms of stoke, the investigation of CAD requires a special CT or MRI sequence called an angiogram. The treatment also differs from other forms of stroke because strong blood thinning anticoagulants may be necessary. With so many twists and turns, it is no wonder CAD rounds up our list of 7 deadly neurological misdiagnoses!

***

Please feel free to disagree with this list, and recommend your own top 7

******