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Advanced Neurology POTS with autonomic storms misdiagnosed as FND

Historically, POTS patients are often misdiagnosed, with (EEG) was negative for epileptiform changes.
a previous study revealing that 83% of nearly 700 patients She was referred to our clinic for abnormal movements,
reported being misdiagnosed with a psychiatric diagnosis and we noted her medical history of chronic back pain
before being accurately diagnosed with POTS. 6 and fatigue. Her neurological examination was significant
Functional neurological disorder (FND) carries for POTS on orthostatic testing, poorly reactive pupils,
diagnostic challenges, with evidence of it being incorrectly hyperreflexia in the patella, and severe small fiber
misdiagnosed in patients with various neurological neuropathy. She was also noted to have postural tremors
conditions, such as multiple sclerosis and POTS. A and occasional myoclonic movements involving her arms,
7,8
previous study has shown that 12% of the included patients, trunk, and legs. POTS was initially suspected following an
having a neurological or an organic somatic disorder, were at-home orthostatic assessment indicating a normal heart
incorrectly diagnosed with FND. Another systematic rate (72 bpm) when supine and tachycardia (126 bpm) when
9
review suggests that FND demonstrates a misdiagnosis standing. The patient received a confirmed diagnosis of
rate of 4%. 10 POTS following a positive tilt table test, showing a >30-point
FND and POTS are both prevalent conditions in increase in heart rate with standing, along with a negative
neurological practice and have similar epidemiological 24-h urine test for metanephrine excretion. The patient was
patterns, as both conditions predominantly affect women initiated on pyridostigmine with a reduction in tremor and
more than men. Myoclonus is a particular symptom that myoclonus events. Further motor improvement occurred
1,7
typically characterizes POTS-related autonomic storms when she was diagnosed and treated for Ehlers–Danlos
and accounts for up to 20% of FND cases. With a shared syndrome, neurogenic bladder, and tethered cord followed
11
12
presentation of this symptom, it is important to differentiate by tethered cord release surgery. The pyridostigmine
between these two conditions and perform necessary tests dose was adjusted and she was prescribed clonazepam to
of orthostatic vitals to avoid a missed diagnosis of POTS. take at the onset of her symptoms. The storms decreased in
frequency on the new regimen.
In this article, we discuss two cases of patients with
POTS who, when presenting to the emergency department Two and a 1/2 years later, the patient started to
(ED) with autonomic storms, were misdiagnosed with experience episodes of limb weakness or paralysis. She
FND. We also review video evidence of both patients’ presented to an external hospital ED and was diagnosed
autonomic storms. Our aim in this review is to highlight with a new FND. Concerned about another error in
the occurrence of autonomic storms associated with diagnosis, the patient presented again to her managing
POTS being misdiagnosed as FND. We also highlight the neurologist, who evaluated her and ran lab testing, which
detrimental impact of incorrectly attributing POTS to a revealed a low potassium of 3.3 mmoL/L. Additional
psychogenic condition, including the delay in appropriate testing revealed hypokalemic periodic paralysis. She was
treatment for autonomic storms. This misdiagnosis initiated on potassium supplementation with a resolution
not only affects patient care but also carries significant of hypokalemic weakness events.
implications for future research.
2.2. Case 2
2. Case presentation An 18-year-old female (she/her) presented to our neurology

2.1. Case 1 clinic with Grave’s disease (post-thyroidectomy), celiac
disease, migraine, and supraventricular tachycardia. She
A 24-year-old female (she/her) initially presented to the had episodes of tachycardia with resting heart rates up
hospital with a diagnosis of FND, reporting dystonia and to 140 bpm to 170 bpm. She also experienced increasing
a burning sensation throughout her muscles (Video S1). dizziness and frequent syncope.
These episodes typically consisted of shaking for a few
minutes, then 15 – 20 min of no activity, followed by Subsequently, the patient had her first episode of
subsequent episodes of shaking. The duration of these myoclonus that lasted about 24 h, characterized by
events ranged from an hour to an entire evening and would substantial full-body twitching. These episodes would
last over hours for 2 – 3 weeks. Thereafter, the patient last about 20 – 30 min and would occur typically in the
reported that the movements would typically decrease in morning, one in the afternoon, and then one before
severity and duration until they disappeared and recurred bedtime, which was the longest. During these episodes,
a few months later. The patient could not find a consistent movement worsened the condition, and she noticed that
trigger for these episodes. Workup with magnetic a substantial amount of walking or exercise during the day
resonance imaging (MRI) of the brain and spine was would result in more severe myoclonic episodes. Right
negative for structural changes, and electroencephalogram before the onset of these events, the patient reported feeling

Volume 4 Issue 2 (2025) 124 doi: 10.36922/an.7653