Functional neurological disorder and multiple sclerosis: a systematic review of misdiagnosis and clinical overlap, Walzl, Stone et al, 2021

[Andy]

Multiple sclerosis (MS) and functional neurological disorder (FND) are both diagnostically challenging conditions which can present with similar symptoms. We systematically reviewed the literature to identify patients with MS who were misdiagnosed with FND, patients with FND who were misdiagnosed with MS, and reports of patients with both conditions. In addition to FND, we included studies of patients with other functional and psychiatric disorders where these caused symptoms leading to investigation for or a diagnosis of MS, which in a different context would likely have been labeled as FND. Our review suggests that MS is one of the most common causes of misdiagnosis of FND and vice versa. We discuss the clinical errors that appear to result in misdiagnoses, such as over-reliance on psychiatric comorbidity when making a diagnosis of FND or over-reliance on neuroimaging for the diagnosis of MS, and practical ways to avoid them. Comorbidity between these two conditions is also likely common, has been poorly studied, and adds complexity to diagnosis and treatment in patients with both MS and FND. Misdiagnosis and comorbidity in a landscape of emerging evidence-based treatments for both MS and FND are issues not only of clinical importance to the care of these patients, but also to treatment trials, especially of MS, where FND could be a hidden confounder.

Open access, https://link.springer.com/article/10.1007/s00415-021-10436-6

My bolding

A 1997 study of 366 patients with a diagnosis of MS referred for a second opinion to Charles Poser found 130 misdiagnosed patients, including 28 (22%) with chronic fatigue syndrome and eight (6%) with “psychiatric disorder” or “post-traumatic syndrome” [32]. Of note, these studies predate the incorporation of MRI into MS diagnostic criteria in 2001 and may be less representative of contemporary misdiagnosis.

In the Scottish Neurological Symptoms Study (SNSS), 9 out of 209 (4%) patients with a diagnosis of MS or demyelination [33] at baseline had an alternative diagnosis at 18 months follow-up, of whom three (33%) had a functional disorder or psychiatric diagnosis at follow-up (anxiety and chronic fatigue syndrome)

 

[Sphyrna]

https://sci-hub.st/10.1016/S0140-6736(05)63920-7
Is that the study by Poser that is referred to? I'd be hard pressed to even call that a study if we can't even look into the methodology used to diagnose CFS. He might've just replaced one misdiagnosis with another.

 

[Woolie]

Comorbidity between these two conditions is also likely common, has been poorly studied, and adds complexity to diagnosis and treatment in patients with both MS and FND.

That doesn't even begin to make sense. How can you have FND - which literally means you have neurological symptoms that are yet to be linked to any neurological disease process - when you have been diagnosed with a neurological disease whose pathophysiology is well understood! And don't tell me its because some of the person's symptoms don't "fit" MS. That's crazy, MS is so incredibly variable in its presentation, there's really no such thing as typical symptoms.

Why use two labels when one can do the job quite nicely?

 

[rvallee]

That doesn't even begin to make sense. How can you have FND - which literally means you have neurological symptoms that are yet to be linked to any neurological disease process - when you have been diagnosed with a neurological disease whose pathophysiology is well understood! And don't tell me its because some of the person's symptoms don't "fit" MS. That's crazy, MS if so incredibly variable in its presentation, there's really now such thing as typical symptoms.

Why use two labels when one can do the job quite nicely?

From people who admonish the use of medical labels, no less. Almost as if it's not a sincere argument.