Answers
1. ECG abnormalities: Prolonged QTc (QT interval corrected for heart rate), 640 milliseconds.
2. CT brain: calcification of bilateral basal ganglion.
3. Blood results:
Total calcium 1.14mmol/l (albumin 41g/L), phosphate 2.79mmol/l (normal 0.87-1.45mmol/L)
Ionized Calcium 0.56mmol/l
PTH <6 pg/ml (normal 15-65pg/ml)
Diagnosis
Severe hypocalcaemia with neurological involvement due to hypoparathyroidism, likely secondary to previous thyroidectomy.
Discussion
Majority of the calcium (99%) is found in bone, and only 1% is found in extracellular fluid. Of this 1%, 50% is in the free (active) ionized form (1-1.15 mmol/L), 40% is bound to protein (predominantly albumin), and 10% is complexed with anions (eg, citrate). Since extracellular calcium concentrations are important for the normal function of muscle and nerve, neuromuscular symptoms are common. For examples, muscle numbness, cramp, spasm and twitching. However, the degree of these neuromuscular symptoms depends on the severity, the rate and the duration of disease. Usually, rapidly falls in calcium are often associated with symptoms. Whereas longstanding hypocalcaemia, like our patient, can be symptomless or presented with mild symptoms only. Seizures can occur in severe cases. Cardiovascular systems may be affected. ECG abnormality like prolonged QT interval can be found in severe cases. Rarely, heart failure can occur also. In case of chronic hypocalcaemia, calcification of the basal ganglia can occur.
In severe hypocalcaemia, likely our patient with seizure and neurological symptoms, prompt replacement of calcium is essential. Intravenous replacement with calcium is the common route of administration. Repeated bolus of calcium gluconate should be given until symptoms relief. ECG monitoring is recommended as arrhythmia can occur. If there is persistent hypocalcaemia or suspicious of hypomagnesaemia, magnesium replacement should be given.
In our case, total 110ml IV 10% calcium gluconate (220mmol elemental calcium) was given. Oral Calcitriol 0.25mcg twice daily, calcium carbonate 1g three times/ day were started. Empirical IV Magnesium sulphate (30mmol) was also given. The patient response well to the treatment with resolution of limbs numbness. No convulsion occur after ICU admission. Serial ECG monitoring found normalization of QTc. Her condition remained stable in ICU and was discharged to general ward for further management 3 days afterward.
References
1. Lorraine A. Fitzpatrick. Hypocalcaemia: Diagnosis and Treatment
2. Christopher B. Beach. Hypocalcaemia. eMedicine
3. Hypocalcaemia. Washington Manual of Medical Therapeutics, 29th ed.,
4. M. Bindu, C.V. Harinarayana. Hypoparathyroidism: A rare treatable cause of epilepsy- report of two cases. EJN 2006; 13: 786-788
5. Dan M. Roden. Long-QT Syndrome. NEJM 2008; 358: 169-76