ISCHEMIC STROKE / STROKE MIMICS
Tetany
Updated on 01/06/2024, published on 04/03/2024
- tetany is a medical condition characterized by an increased excitability of neuronal and muscle membranes
- hyperexcitability occurs at all levels of the nervous system, including the central nervous system
- tetany presents with extremely diverse clinical symptoms and can result from various underlying causes that disrupt the normal balance of calcium and other electrolytes in the body
- a tetanic seizure (hands and feet crumps with limb paresthesia) is clinically the most notable symptom of tetany
- other typical symptoms include:
- fatigue and irritability
- palpitations
- tingling, burning
- chronic cramps
- acute hypocalcemia is a medical emergency and, unless treated promptly, may progress to bronchospasm and cardiovascular instability (Sehgal, 2011)
- muscle spasms caused by tetanus are not classified as tetany
- some manifestations of tetany can resemble a stroke (so it is classified as a potential stroke mimic)
Etiopathogenesis
- the primary cause of tetany is electrolyte imbalance (most commonly hypocalcemia, but also hypomagnesemia), which rapidly and significantly increases the excitability of neuronal and muscle membranes
Hypocalcemia
- tetany most commonly occurs when the total serum calcium is decreased (corrected calcium is standard laboratory value)
- hypocalcemia is defined as total serum calcium level < 8.5 mg/dL (2.12 mmol/L) or ionized calcium level < 4.4 mg/dL (1.1 mmol/L)
- in clinical signs of tetany occur and no evident abnormality in standard ionogram (Ca, Cl, K, Na, Mg) are detected, ionized calcium levels must be determined (Alanazi, 2023)
- decreased ionized calcium levels are caused by increased calcium binding to albumin, usually provoked by hyperventilation ⇒ typical cause of “normocalcemic” tetany
- the corrected (total) calcium may need to be raised above the normal range to maintain normal ionized calcium in the context of metabolic alkalosis
- ionized Ca levels are not always available; if clinical tetany occurs, start supplementation therapy despite normal total calcium in serum
- factors that determine the severity of symptoms include acid-base status (hypocalcemia and alkalosis act synergistically)
Normocalcemic tetany
- most “normocalcemic” tetany attacks are caused by undetected hypocalcemia
- tetany due to hypomagnesemia is a complex metabolic disturbance characterized by hypomagnesemia (plasma total magnesium< 1.5 mg/dL [< 0.65 mmol/L]) leading to hyperexcitability, muscular spasms, seizures, respiratory distress, etc. (Unandh, 2021)
- another possible cause of normocalcemic tetany is a paraneoplastic syndrome (probably mostly due to secondary hypocalcemia) (Partanen, 1980)
- hypocalcemia refers to a condition characterized by low levels of corrected (total) calcium in the blood
- calcium is an essential mineral involved in various physiological processes, including muscle contraction, nerve transmission, blood clotting, and bone formation
- hypocalcemia can result from several underlying causes
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- corrected calcium and ionized calcium are two different measures of calcium levels in the blood
- corrected calcium accounts for albumin levels (as calcium binds to albumin ) and provides a more accurate total calcium level
- ionized calcium measures the free, biologically active form of calcium in the blood; it represents the fraction of calcium that is readily available for physiological functions
- in tetany, the focus is often on the ionized calcium level because it reflects the biologically active form of calcium that directly affects neuromuscular excitability
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Clinical Presentation
Tetanic seizure
- seizures occur spontaneously or as a result of excitement or other provoking moments
- they last ~ 5-20 minutes, the patient is fully conscious but restless, and the seizure is accompanied by autonomic reactions, tachycardia, sweating, sometimes nausea, and global discomfort
- typical signs:
- sensory manifestations – paresthesia and tingling of the hands and feet, perioral numbness, gradually increasing in extent and intensity
- carpopedal spasms
- with extension of the interphalangeal joints and adduction and flexion of the metacarpophalangeal joints
- bronchospasm, laryngospasm, or generalized tonic muscle contractions in severe cases (must be distinguished from generalized seizures)
- seizure may be accompanied by hyperventilation, which accentuates its course by inducing respiratory alkalosis and hypocapnia (in susceptible individuals, a tetanic seizure can be provoked by voluntary hyperventilation alone)
Other manifestations of increased neuromuscular excitability
- increased deep tendon reflexes
- neurovegetative lability, e.g., positive dermographism
- signs of increased neuromuscular excitability
- Chvostek’s sign – contraction of the ipsilateral facial muscles, particularly the upper lip, in response to tapping or percussing the facial nerve just anterior to the ear
- Trousseau’s sign – carpal spasm (flexion of the wrist and metacarpophalangeal joints, extension of the interphalangeal joints) induced by inflating a blood pressure cuff on the upper arm above systolic pressure for 3-5 minutes
- it may also be induced by voluntary hyperventilation for one to two minutes after releasing the cuff
- both signs may be negative in hypocalcemic patients and, vice versa, may occur in healthy individuals (Chvostek’s sign in ~10%)
In addition, there are a lot of less specific symptoms of increased neuromuscular excitability, such as:
- headaches
- chest pain, palpitations
- in case of negative coronary findings, EMG for tetany should be performed, and appropriate therapy should be administered
- hyperirritability, anxiety, and moodiness
- fatigue
- decreased concentration and work performance
- persistent or intermittent paresthesias of the limbs and around the mouth
- hyperhidrosis
- sleep disturbance
Diagnostic evaluation
- EMG
- spontaneous motor activity with short-duration, high-frequency motor unit action potentials, especially in small hand muscles after provoking tests (limb ischemia, hyperventilation)
- nerves and muscles may show increased sensitivity to electrical stimulation during nerve conduction studies, resulting in lower thresholds for evoking muscle responses
- motor unit recruitment patterns may remain relatively normal or decrease during voluntary muscle contractions
- EEG – abnormal, nonspecific
- repeated examination of ionogram, incl. ionized fractions of Ca2+ and Mg 2+
- Ca2+ 4.5-5.3 mg/dL (1.15-1.35 mmol/L), total Ca 8.6-10.2 mg/dL (2.2-2.61 mmol/L)
- psychological examination
- if hypocalcemia or hypomagnesemia is detected, search for its cause
Management
Management of acute tetanic seizure
- calcium gluconate or chlorate IV 10 mL
- 10% magnesium sulfate IV or IM 10 mL – if hypomagnesemia contributes to tetany
- short-acting sedatives may be added – alprazolam, diazepam, bromazepam
Management of the cause of hypocalcemia
- starting vitamin D supplementation, treating hypoparathyroidism, renal failure, malabsorption syndromes, or other medical conditions contributing to hypocalcemia, etc.
Management of other symptoms
- lifestyle changes (it is recommended to avoid stress and other triggers of hyperventilation and to increase calcium intake)
- Mg2+ and Ca2+ supplements + monitoring of calcium levels
- consider short-term treatment with mild sedatives (weeks to months) – Diazepam, Oxazepam, Alprazolam
- carbamazepine (Tegretol, Biston) 300-600mg per day for severe or frequent seizures (hypocalcemia and hypomagnesemia must be corrected)
- psychotherapy