Description

Effective treatment of epilepsy depends on apt characterisation of the semiology and aetiology identification. However, this can be difficult as most epilepsy are idiopathic in nature and workup is generally unrevealing. Nevertheless, investigations such as plain CT brain, serum electrolytes and urine toxicology are typically the routine. In a resource-limited setting, this is only occasionally feasible and potentially correctable aetiologies are missed.

We report the case of a woman in her 20s who was previously diagnosed with idiopathic generalised epilepsy in her late teens. She was started on 50 mg lamotrigine once daily. No CT brain or serum electrolyte investigation was done, and the patient was merely followed up in her local health clinic. Her epilepsy was deemed well controlled until her presentation this year to our casualty with two consecutive episodes of ‘seizures’. Chvostek and Trousseau signs were noted on arrival (no images were taken as the patient was in severe distress). The patient was of normal height (165 cm) and weight (55 kg), with no skeletal or dental deformities. The classical feature of pseudohypoparathyroidism, Archibald sign, was absent as her fourth and fifth digits were of normal length, without any dimpling over the fourth or fifth knuckles on a clenched fist. Her cardiovascular and pulmonary examinations were normal and there were no neurological deficits; also, no skin rashes, periungual fibromas and angiokeratomas were seen. Routine laboratory investigations confirmed profound hypocalcaemia (corrected calcium: 0.7 mmol/L, normal range 2.25–2.62 mmol/L) and hyperphosphataemia (PO4: 2.4 mmol/L, normal range 1.1–1.8 mmol/L). Her symptoms improved remarkably with intravenous calcium infusion. A non-contrast CT brain revealed diffuse intracranial calcifications (see figure 1). The semiology of the seizures, past and present, was clarified. During these episodes, she experienced limb weakness and spasms, perioral numbness, and difficulty speaking (laryngospasm). Additionally, she was fully conscious during these episodes and could vividly recall the events. No tonic-clonic movements were noted by her family, nor did she experience any postictal drowsiness or tongue biting. Overall, these features were inconsistent with epilepsy. Further investigations revealed a low intact Parathyroid Hormone (iPTH: 0.58 pmol/L, normal range 1.58–6.03 pmol/L) and low 24-hour urine calcium (0.2 mmol/24 hours; normal range 2.5–7.5 mmol/24 hours). These results confirmed a diagnosis of hypoparathyroidism that was previously not identified. She was started on oral calcium carbonate 1.5 g three times per day, oral calcitriol 0.5 μg two times per day and weaned off lamotrigine. To date, her calcium levels have remained stable (corrected calcium range: 2.0–2.1 mmol/L, recommended treatment range: 2.0–2.1 mmol/L) and she has since reported no more seizures.

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Figure 1

CT brain revealing diffuse basal ganglia, thalamic and cerebellar calcification.

The causes of hypoparathyroidism are diverse, ranging from postsurgical thyroidectomy, autoimmune and infiltrative diseases, and radiation damage to abnormal development of the parathyroid tissue. It can also be idiopathic. Extensive workup for hypoparathyroidism is not available in our local setting. The main focus of management rests solely on adequate replacement of calcium and phosphate. Treatment with calcium and vitamin D analogues might result in hypercalciuria, nephrocalcinosis and nephrolithiasis. As such, monitoring of renal function, serum calcium and 24-hour urine calcium is important.1

At the outset, as our patient has no family history of epilepsy and no neurocutaneous manifestations (such as café au lait spots, shagreen patches or periungual fibromas), her seizures were assumed to be idiopathic generalised epilepsy in nature. While separate clinical entities, features in hypocalcaemia such as Chvostek, Trousseau signs and laryngospasm can sometimes be misinterpreted as generalised tonic-clonic seizures.2 A review of our patient’s previous records also revealed no baseline CT brain or serum electrolytes such as calcium, phosphate or magnesium. As such, the diagnosis of hypoparathyroidism was not made for years until the present admission. Identification and treating the root of the problem, hypocalcaemia, is imperative as antiepileptic drugs will not improve outcomes, exposing patients to unnecessary pill burden and further side effects.3 4

In our patient, years of prolonged hypocalcaemia due to hypoparathyroidism resulted in extensive basal ganglia, cerebellar and thalamic calcification. While intracranial calcifications are generally benign, some patients may develop neuropsychological dysfunctions. When this occurs, patients are said to have Fahr syndrome, an irreversible neurodegenerative disorder characterised by seizures, parkinsonism and dementia with intracranial calcification. The extent of calcification on CT brain, however, correlates poorly with the clinical manifestation of Fahr syndrome. As seen in our patient’s CT brain, despite the extensive intracranial involvement, she was still cognitively intact, able to carry out her daily activities as a school teacher, do housework and maintain a good relationship with her family. The development of Fahr syndrome is thus variable. Clinicians have to be vigilant in the treatment of prolonged hypocalcaemia and monitor patients for this potential complication.5 MRI brain is also a valuable imaging in epileptic workup as it may identify any subtle structural causes of epilepsy, which might not be easily identified in CT brain.