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Medical condition, exhibiting involuntary contraction of muscles
Medical condition
Look up
tetany
in Wiktionary, the free dictionary.
Tetany
or
tetanic
seizure
is a
medical sign
consisting of the involuntary contraction of
muscles
, which may be caused by disorders that increase the
action potential
frequency of muscle cells or of the nerves that innervate them.
Muscle cramps caused by the disease
tetanus
are not classified as tetany; rather, they are due to a lack of inhibition to the neurons that supply muscles.
Tetanic contractions
(physiologic tetanus) have a broad range of
muscle contraction
types, of which tetany is only one.
Signs and symptoms
[
edit
]
Position of Hands in the Spasm of Tetany (1905)
Tetany is characterized by contraction of distal muscles of the hands (carpal spasm with extension of interphalangeal joints and adduction and flexion of the metacarpophalangeal joints) and feet (pedal spasm) and is associated with tingling around the mouth and distally in the limbs.
[
citation needed
]
Causes
[
edit
]
Cow grazing on rapidly grown pasture with tetany of the neck suggesting
grass tetany
[1]
Metabolic alkalosis with hypokalemia like
Gitelman syndrome
and
Bartter syndrome
can cause tetany. Vomiting induced alkalosis and hyperventilation induced respiratory alkalosis also cause tetany because of neuronal irritability.
[
citation needed
]
Pathophysiology
[
edit
]
Hypocalcemia
is the primary cause of tetany. Low ionized calcium levels in the
extracellular fluid
increase the permeability of neuronal membranes to sodium ion, causing a progressive depolarization, which increases the possibility of action potentials. This occurs because calcium ions interact with the exterior surface of
sodium channels
in the
plasma membrane
of
nerve cells
and hypocalcemia effectively increases
resting potential
(rendering the cells more excitable) since less positive charge is present extracellularly. When calcium ions are absent the voltage level required to open voltage gated sodium channels is significantly altered (less excitation is required).
[7]
If the plasma Ca
2+
decreases to less than 50% of the normal value of 9.4 mg/dl, action potentials may be spontaneously generated, causing contraction of peripheral skeletal muscles. Hypocalcemia is not a term for tetany but is rather a cause of tetany.
Diagnosis
[
edit
]
French Professor
Armand Trousseau
(1801?1867) devised the maneuver of occluding the
brachial artery
by squeezing, to trigger cramps in the fingers. This is now known as the
Trousseau sign of latent tetany
.
[8]
Also, tetany can be demonstrated by tapping anterior to the ear, at the emergence of the facial nerve. A resultant twitch of the nose or lips suggests low calcium levels. This is now known as the
Chvostek sign
.
[
citation needed
]
EMG studies reveal single or often grouped motor unit discharges at low discharge frequency during tetany episodes.
[
citation needed
]
References
[
edit
]
- ^
Bill Kvasnicka; Les J. Krysl. "Grass Tetany in Beef Cattle".
Beef Cattle Handbook
(PDF)
.
- ^
Haldimann, B.; Vogt, K. (Sep 1983). "[Hyperphosphatemia and tetany following phosphate enema]".
Schweiz Med Wochenschr
.
113
(35): 1231?3.
PMID
6623048
.
- ^
Sutters, M.; Gaboury, CL.; Bennett, WM. (Oct 1996). "Severe hyperphosphatemia and hypocalcemia: a dilemma in patient management".
J Am Soc Nephrol
.
7
(10): 2056?61.
doi
:
10.1681/ASN.V7102056
.
PMID
8915965
.
- ^
Hall, John, ed. (2010).
Guyton and Hall textbook of medical physiology
(12th ed.). Philadelphia, Pa.: Saunders/Elsevier. p. 367.
ISBN
978-1-4160-4574-8
.
- ^
Hall, John, ed. (2010).
Guyton and Hall textbook of medical physiology
(12th ed.). Philadelphia, Pa.: Saunders/Elsevier. p. 856.
ISBN
978-1-4160-4574-8
.
- ^
Grobin, W (May 14, 1960).
"A New Syndrome, Magnesium-Deficiency Tetany"
.
Canadian Medical Association Journal
.
82
(20): 1034?5.
PMC
1938332
.
PMID
20326284
.
- ^
Hall, John, ed. (2010).
Guyton and Hall textbook of medical physiology
(12th ed.). Philadelphia, Pa.: Saunders/Elsevier. p. 64.
ISBN
978-1-4160-4574-8
.
- ^
Hernandez, Anna.
"MD"
(html)
.
Osmosis.org
. The Internet Archive: Elsevier.
Archived
from the original on 2021-11-29
. Retrieved
2022-03-31
.
Trousseau's sign refers to the involuntary contraction of the muscles in the hand and wrist (i.e., carpopedal spasm) that occurs after the compression of the upper arm with a blood pressure cuff.
External links
[
edit
]
- Maccallum, WG; Voegtlin, C (Jan 9, 1909).
"On the relation of tetany to the parathyroid glands and to calcium metabolism"
.
The Journal of Experimental Medicine
.
11
(1): 118?51.
doi
:
10.1084/jem.11.1.118
.
PMC
2124703
.
PMID
19867238
.
- Williams, A; Abraham, D; Liddle, V (2011).
"Tetany: A diagnostic dilemma"
.
Journal of Anaesthesiology Clinical Pharmacology
.
27
(3): 393?394.
doi
:
10.4103/0970-9185.83691
.
PMC
3161471
.
PMID
21897517
.
- Harrison's Principles of Internal Medicine 16th Edition ? Dennis L. Kasper, Eugene Braunwald, Stephen Hauser, Dan Longo, J. Larry Jameson, Anthony S. Fauci.