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LETTER TO EDITOR
Year : 2015  |  Volume : 63  |  Issue : 5  |  Page : 772-774

Andersen-Tawil syndrome: A review of literature


1 Department of Neurology, St Stephen's Hospital, Tis Hazari, New Delhi, India
2 Department of Medicine, St Stephen's Hospital, Tis Hazari, New Delhi, India
3 Metropolis Labs, Allapuzha, Kerala, India

Date of Web Publication6-Oct-2015

Correspondence Address:
Gaurav Bhaskar Nigam
Department of Medicine, St Stephen's Hospital, Tis Hazari, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.166530

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How to cite this article:
Babu SS, Nigam GB, Peter C S, Peter C S. Andersen-Tawil syndrome: A review of literature. Neurol India 2015;63:772-4

How to cite this URL:
Babu SS, Nigam GB, Peter C S, Peter C S. Andersen-Tawil syndrome: A review of literature. Neurol India [serial online] 2015 [cited 2019 Aug 18];63:772-4. Available from: http://www.neurologyindia.com/text.asp?2015/63/5/772/166530


Sir,

A 25-year old male, born of non-consanguineous marriage, with a normal antenatal, perinatal, and developmental history and no family history of neurological illness, presented with repeated episodes of weakness involving proximal and distal muscles of bilateral upper and lower limbs. These episodes started occurring at around 17 years of age, each lasting for about 24 hours with spontaneous recovery. The severity varied from moderate-to-severe, requiring support from friends and relatives for all activities. The frequency was 4-5/month and remained unchanged over the years. None of these episodes was associated with bulbar, facial or respiratory muscle weakness, or sensory or bladder involvement. These episodes usually occurred in the late evening, while resting or after a heavy meal. There was no obvious relationship with exercise or exposure to cold. He also reported intermittent, fast and regular palpitations lasting for seconds to minutes especially during the periods of weakness, not associated with presyncope or syncope.

On examination, he had a pulse rate of 80/min and a blood pressure of 120/70 mmHg. Micrognathia, retrognathia, and small ears [Figure 1] were observed along with bilateral clinodactyly.
Figure 1: Retrognathia and micrognathia in a patient with Anderson-Tawil syndrome

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The cardiovascular examination was normal. The neurological examination was unremarkable except for mild bilaterally symmetrical, proximal muscle weakness.

Nerve conduction studies revealed normal conduction velocities, distal latencies and compound muscle action potential (CMAP) amplitudes. In all the tested nerves, the f-wave latencies and sensory conduction were also normal. Electromyography revealed potentials with small amplitudes and short duration but without polyphasia. Recruitment was early and interference was full. After 10 s of exercise, stimulation of abductor digiti minimi (ADM) did not reveal any abnormalities over the next 2 min. However, after the long exercise test of 5 min, the CMAP amplitude was found to decrease exponentially over the next 40 min. The calculated decrement was 47% compared to the maximal CMAP amplitude [Figure 2].
Figure 2: Long-exercise protocol showing a decrement of 47%

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His electrocardiogram was normal and the QT interval was not prolonged. Echocardiogram did not show structural abnormalities. A twenty-four hour Holter monitoring was planned in view of the history of intermittent palpitations. Ultrasound abdomen showed normal kidneys. Estimation of serum sodium, potassium, calcium, magnesium, and thyroid hormones revealed normal values. Creatine phosphokinase was mildly elevated (313 IU/L).

Anderson-Tawil syndrome (ATS) is a clinical entity characterized by a triad of episodic flaccid muscle weakness (periodic paralysis), ventricular arrhythmia with prolonged QT interval, and skeletal anomalies.[1],[2]

Neurological presentation most commonly seen with ATS is an episodic weakness of skeletal muscles in a generalized pattern with sparing of bulbar and respiratory musculature. Reflexes may be absent or diminished during the episodes of weakness. Mild persistent weakness is also fairly common. Learning disabilities and febrile seizures are the other known neurological associations seen in only a small minority of cases. The attacks are commonly precipitated by exertion, or following a period of rest after the exertion. Variable association with intake of heavy carbohydrate meals and potassium rich foods have been described. In the present report, sleep, rest after exertion and a heavy meal, usually a non-vegetarian one, were the precipitating factors.[2],[3]

Skeletal anomalies in the syndrome are micrognathia, retrognathia, clinodactyly, syndactyly, low set ears and hypertelorism. The first three of these anomalies were observed in the present case.[1],[2],[4] Classical electrocardiac abnormalities include prominent Q waves, prolonged QT and QU intervals, ventricular arrhythmias like premature ventricular contractions, polymorphic ventricular tachycardia and bi-directional ventricular tachycardia that may be evident on routine electrocardiogram or may require a 24-hour Holter monitoring. Structural abnormalities like dilated cardiomyopathy are infrequently reported. A hypoplastic kidney and renal tubular defects may be seen in rare cases.[2],[5]

Electrophysiological evaluation of the nerves is of great diagnostic value, as abnormalities are seen in about 80% of the cases with sensitive testing. The long exercise protocol of 5 min maximal exercise followed by the compound action muscle potential (CMAP) recording at 1 min, and then after a 5 min interval for 40 min, demonstrates more than 40% decrement after an initial increase in the CMAP amplitude.[3] In this report, recording of the abductor digiti minimi (ADM) muscle showed a 47% decrement consistent with the diagnosis. Genetic testing for KCNJ2 gene encoding the inward rectifier channel 2 protein is positive in about 40% of patients with ATS, especially in those with a positive family history.[6]

The management plan in ATS would be to prevent or ameliorate the number of attacks by avoidance of precipitating factors and by the use of carbonic anhydrase inhibitors like acetazolamide and dichlorophenamide. The regular use of slow-release potassium supplements can be helpful in patients prone to developing hypokalemia. Cardiac involvement, especially in symptomatic cases, requires the long-term use of antiarrhythmic drugs like flecainide or implantation of a cardioverter-defibrillator.[2],[4]

The case described here had the classical neurological presentation of periodic paralysis in ATS with a few atypical features like pain and stiffness of muscles and association with a nonvegetarian (high carbohydrate, high-protein) meal. The attacks were also very stereotypical, and the frequency was stable over a period of 8 years. This report also highlights the role of post-exercise CMAP recording in the diagnosis of this entity. The presence of the characteristic skeletal abnormalities helps in reinforcing the diagnosis, which highlights the importance of a careful physical examination in all patients presenting with periodic paralysis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Tawil R, Ptacek LJ, Pavlakis SG, DeVivo DC, Penn AS, Ozdemir C, et al. Andersen's syndrome: Potassium-sensitive periodic paralysis, ventricular ectopy, and dysmorphic features. Ann Neurol 1994;35:326-30.  Back to cited text no. 1
    
2.
Statland JM, Tawil R, Venance SL. Andersen-Tawil Syndrome. Gene Reviews. Initial Posting: November 22, 2004. [Last update on 2013 Jan 03]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK1264.  Back to cited text no. 2
    
3.
Tan SV, Matthews E, Barber M, Burge JA, Rajakulendran S, Fialho D, et al. Refined exercise testing can aid DNA-based diagnosis in muscle channelopathies. Ann Neurol 2011;69:328-40.  Back to cited text no. 3
    
4.
Donaldson MR, Yoon G, Fu YH, Ptacek LJ. Andersen-Tawil syndrome: A model of clinical variability, pleiotropy, and genetic heterogeneity. Ann Med 2004;36 Suppl 1:92-7.  Back to cited text no. 4
    
5.
Schoonderwoerd BA, Wiesfeld AC, Wilde AA, van den Heuvel F, Van Tintelen JP, van den Berg MP, et al. A family with Andersen-Tawil syndrome and dilated cardiomyopathy. Heart Rhythm 2006;3:1346-50.  Back to cited text no. 5
    
6.
Lange PS, Er F, Gassanov N, Hoppe UC. Andersen mutations of KCNJ2 suppress the native inward rectifier current IK1 in a dominant-negative fashion. Cardiovasc Res 2003;59:321-7.  Back to cited text no. 6
    


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