Malignant Hyperthermia and Its Connection to Periodic Paralysis
By Susan Q. Knittle-Hunter, Periodic Paralysis Network, Inc.
Malignant Hyperthermia (MH) is a rare but life-threatening reaction to
certain anesthetic agents. Many people with Periodic Paralysis (PP) have never
been warned about this danger, yet it is essential information for patients,
families, and medical professionals — especially because many in the PP
community cannot tolerate anesthesia or medications at all.
Below is a clear explanation of what MH is and how it relates to the
channelopathy behind Periodic Paralysis.
What Is Malignant Hyperthermia?
Malignant Hyperthermia is a genetic disorder of skeletal muscle
calcium regulation. It is triggered by:
- Certain general anesthetics (such as volatile gases)
- Succinylcholine, a commonly used muscle relaxant
When exposed to a trigger, the person’s muscles release uncontrolled
amounts of calcium, causing the muscle cells to go into overdrive. This
leads to:
- Rapid rise in body temperature
- Severe muscle rigidity
- Dangerous heart rhythm
abnormalities
- Breakdown of muscle tissue
(rhabdomyolysis)
- Life-threatening metabolic crisis
MH is considered a medical emergency requiring immediate treatment
with dantrolene and intensive care support.
The main genes associated with MH are RYR1 and CACNA1S.
Both are ion-channel genes responsible for calcium handling in muscle cells.
How Is Malignant Hyperthermia
Connected to Periodic Paralysis?
Although MH and PP are not the same condition, they share several
important connections:
1. Both Are Ion Channel Disorders
(Channelopathies)
Periodic Paralysis is caused by defects in ion channels — often sodium,
potassium, or calcium channels — including the SCN4A gene that many PP
patients carry.
MH involves RYR1 and CACNA1S, which also regulate calcium flow in
muscle cells.
Because these systems work together, dysfunction in one can affect the
others.
2. Some PP Mutations Create
Overlapping Risk
Certain calcium-channel mutations have been linked to both:
- Hypokalemic PP
- Malignant Hyperthermia
susceptibility
This means that people with PP — especially those with calcium-channel
variants — may be at higher risk for MH during anesthesia.
Even those with sodium-channel disorders like Andersen-Tawil Syndrome or
Hyperkalemic PP have increased anesthetic sensitivity, arrhythmia risk, and
metabolic instability, which can resemble or trigger MH-like crises.
3. Many PP Patients Cannot Tolerate
Standard Anesthesia
In her books, Susan describes that PP is not simply “muscle weakness”; it
is a mineral metabolic disorder that affects how muscle cells handle
sodium, potassium, and calcium.
Because anesthesia drugs affect these same minerals and the electrical activity
of muscle membranes, PP patients often experience:
- Sudden paralysis
- Dangerous potassium shifts
- Heart arrhythmias
- Respiratory depression
- Severe metabolic reactions
These reactions can look very similar to Malignant Hyperthermia — and in
some cases, anesthesia can trigger MH directly.
4. Both Conditions Can Be Fatal If Not
Properly Managed
For both PP and MH, the medical community often lacks understanding,
misdiagnoses are common, and patients may face disbelief or gaslighting when
they report anesthesia sensitivity.
This is especially true for PP patients whose symptoms do not fit common
medical models.
Your lived experience and research have repeatedly shown:
“Any PP patient can have a severe, life-threatening reaction to
anesthesia — whether or not they meet the textbook definition of Malignant
Hyperthermia.”
> Susan Q. Knittle-Hunter, Living With Periodic Paralysis
Why PP Patients Must Treat MH
Precautions Seriously
Even though MH is genetically separate from PP, the overlap in ion
channel instability, the shared calcium-regulation issues, and the severe
anesthesia risks mean:
All PP patients should be considered
MH-susceptible unless proven otherwise.
This is consistent with your books, your decades of research, and
countless experiences from PP patients around the world who suffered
catastrophic reactions after anesthesia.
Practical Safety Steps for People With
PP
1. Wear medical alert identification
Include:
“Periodic Paralysis — Channelopathy. No anesthesia. MH risk.”
2. Avoid triggering anesthetics
This includes succinylcholine and volatile anesthetic gases
used in general anesthesia.
3. Request non-triggering alternatives
If absolutely necessary, anesthesia should be handled by experts using
MH-safe methods, with close electrolyte and cardiac monitoring.
4. Bring written documentation
Susan’s books, emergency documents, and the PPNI medical emergency card
can be invaluable during hospital visits.
5. Ensure all doctors understand PP as
a metabolic disorder
Not a neuromuscular disease, not a psychiatric problem, and not
“anxiety.”
Understanding the mineral metabolic instability is the key to safe care.
Conclusion
Malignant Hyperthermia is rare — but for people with Periodic Paralysis,
the overlap in muscle-cell calcium regulation and anesthesia sensitivity makes
it a critical topic. Whether or not a PP patient has a known MH mutation, the
risk is real, and proper precautions can prevent tragedy.
Raising awareness, educating providers, and empowering patients is
essential — and Susan’s work, has been leading this effort for years.
References
Knittle-Hunter, S.Q.
- Living With Periodic Paralysis:
The Mystery Unraveled
- What Is Periodic Paralysis? A
Disease Like No Other
- The Periodic Paralysis Guide
& Workbook: Be the Best You Can Be Naturally
- A Bill of Rights for Periodic
Paralysis Patients
- PPNI Blog Archives (various
articles on anesthesia, metabolic instability, and emergency care)
Additional Non-Organizational Medical Sources (approved):
- Rosenberg H., et al. “Malignant
Hyperthermia.” Orphanet Journal of Rare Diseases.
- StatPearls: “Malignant
Hyperthermia.”
- Kalbitz M., et al. “Ion Channel
Disorders and Anesthesia Sensitivity.” Journal of Cli
Picture: Operating Room
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