1 Service of Bone Diseases (WHO Collaborating Center for Osteoporosis Prevention), Department of Rehabilitation and Geriatrics, 2 Service of Nephrology, Department of Internal Medicine and 3 Thoracic Surgery Unit, Department of Surgery, University Hospital of Geneva, Switzerland
Correspondence and offprint requests to: René Rizzoli, MD, Service of Bone Diseases, Department of Rehabilitation and Geriatrics, University Hospital of Geneva, CH-1211 Geneva 14, Switzerland. Email: Rene.Rizzoli{at}medecine.unige.ch
Keywords: chronic renal failure; extraocular muscles; parathyroid surgery; tetany
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Introduction |
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To illustrate this association, we report on three patients who, following PTX for severe hyperparathyroidism, experienced acute hypocalcaemia and thereafter transient diplopia, a rare complication of hypocalcaemia.
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Cases |
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Case 2
This patient was a 26-year-old woman with end-stage renal failure secondary to reflux nephropathy, on maintenance HD since 1995. A subtotal PTX was performed in June 2003 for secondary hyperparathyroidism with a very high serum PTH (453 pmol/l) and serum alkaline phosphatase levels (632 U/l; normal range: 32104 U/l), although the protein-corrected serum calcium level was normal (2.28 mmol/l). At the time of surgery, she was receiving 1200 mg elemental calcium and 0.25 µg calcitriol a day. The day after surgery, she experienced very transient diplopia with dysesthesia and muscle cramps. At that time, ophthalmological and neurological evaluations were normal, but Chvostek's and Trousseau's signs were present. A marked decrease in serum calcium to 1.74 mmol/l, with a possible hungry bone syndrome (the intact PTH level was 32 pmol/l), developed the day after surgery. Laboratory investigation also revealed hyperphosphataemia (2.02 mmol/l) and hyperkalaemia (7.2 mmol/l; normal range: 3.64.6 mmol/l), although magnesium concentration was normal (0.79 mmol/l; normal range: 0.651.05 mmol/l), as was the bicarbonate level. After intravenous administration of large amounts of calcium gluconate (10%) and oral calcium over the next 24 h, the level of serum calcium became normal and the symptoms disappeared.
Case 3
The third patient was a 42-year-old man with pre-dialysis renal failure secondary to obstructive nephropathy. In January 2000, he underwent a total PTX with autotransplantation for severe hyperparathyroidism [intact PTH: 132 pmol/l; protein-corrected serum calcium: 2.20 mmol/l; high levels of alkaline phosphatase: 403 U/l (normal range: 98279 U/l)]. At that time, he was receiving 1.5 µg calcitriol once a day. Hypocalcaemia developed 24 h after surgery. Despite the introduction of a large dose of calcium (12 g per day) and increasing the dose of calcitriol to 2 µg per day, 10 days after surgery he complained of paresthesiae of the distal extremities and circum-oral area, Chvostek's and Trousseau's signs and muscle cramps. He also complained of transient diplopia, but clinical examination revealed no abnormalities. Laboratory investigations on readmission after surgery showed marked hypocalcaemia (1.32 mmol/l), hyperphosphataemia (2.17 mmol/l) and hypomagnesaemia (0.57 mmol/l). Hypoparathyroidism was diagnosed on the basis of low levels of PTH in the serum (1.1 pmol/l). With calcium supplements and active vitamin D derivatives, the serum calcium increased slowly and became normal within 1 week.
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Discussion |
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Diplopia in these cases was most probably a manifestation of tetany of the extraocular muscles induced by hypocalcaemia. Acute hypocalcaemia directly increases peripheral neuromuscular irritability [3]. The primary determinants of symptoms and signs in patients with hypocalcaemia are related to the kinetics and relative change of serum calcium. PTX performed on these patients led to a marked decrease in serum calcium within a few days of the operation.
Other factors could contribute to this clinical presentation, including the acidbase status (although no such modifications were observed), magnesium depletion, a potassium imbalance and emotional stress after surgery, all of which could affect epinephrine concentrations and elicit tetany in patients with hypocalcaemia [4].
Classically, tetany can affect all muscles except the extraocular ones [5]. Nevertheless, diplopia has been observed in patients with hypocalcaemia. For example, a report described a 15-year-old boy complaining of attacks of a thick tongue, double vision and heart failure. He was diagnosed as having idiopathic hypoparathyroidism with marked hypocalcaemia (1.09 mmol/l) [6]. Another report described a 74-year-old male with idiopathic hypoparathyroidism revealed by a non-insulin-dependent diabetes mellitus and severe hypocalcaemia (1.6 mmol/l) [7]. However, to our knowledge, diplopia was not observed after PTX. An article published in 1960 stated that patients with severe hypocalcaemia after a subtotal PTX for renal hyperparathyroidism could experience blurring of vision and difficulty in accommodation [8].
These case reports raise the question of prevention of post-PTX hypocalcaemia. Given the frequency of this complication, a daily follow-up of serum calcium is mandatory. Pre-operative administration of calcitriol to all such patients if they are not already being treated with a vitamin D metabolite should be recommended as well as early administration of high doses of oral calcium. Accordingly, a clinical algorithm has been proposed recently [9].
In conclusion, diplopia is a rare manifestation of acute hypocalcaemia and should be noted as a potential complication of PTX in dialysis patients. Although rare, if this complication were made known to nephrologists it could avoid unnecessary neurological investigations.
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Acknowledgments |
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Conflict of interest statement. None declared.
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References |
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