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ORIGINAL ARTICLE
Year : 2007  |  Volume : 14  |  Issue : 2  |  Page : 51-53 Table of Contents     

A comparison between the ice test and single-fiber electromyography (SFEMG) in the diagnosis of ptosis caused by myasthenia gravis


1 Department of Ophthalmology, Cairo University, Cairo, Egypt
2 Department of Neurology, Cairo University, Cairo, Egypt

Date of Web Publication11-Nov-2009

Correspondence Address:
Essam A El-Toukhy
14-A El-Sobki Street #23, Dokki, Cairo-12311
Egypt
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Source of Support: None, Conflict of Interest: None


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   Abstract 

Purpose. To compare the results of the ice test with those attained with single-fiber electromyography (SFEMG) in the diagnosis of ocular myasthenia gravis (MG).
Patients and Methods. Ice was placed on the upper lids of 14 patients (10 females, 4 males) with ptosis who were suspected of having MG; the change in lid height was noted. After SFEMG was performed, the results of the 2 tests were then compared.
Results. A positive response to the ice test was elicited in 12 (85.7%) patients. All 12 patients with a positive ice test had abnormal SFEMG findings. Both patients with a negative ice test had normal SFEMG findings.
Conclusion. A positive response to the ice test is a sensitive method of diagnosing ptosis caused by MG and correlates well with SFEMG testing.

Keywords: myasthenia gravis, ice test, electromyography, ptosis


How to cite this article:
El-Toukhy EA, Hosni HH. A comparison between the ice test and single-fiber electromyography (SFEMG) in the diagnosis of ptosis caused by myasthenia gravis. Middle East Afr J Ophthalmol 2007;14:51-3

How to cite this URL:
El-Toukhy EA, Hosni HH. A comparison between the ice test and single-fiber electromyography (SFEMG) in the diagnosis of ptosis caused by myasthenia gravis. Middle East Afr J Ophthalmol [serial online] 2007 [cited 2019 Dec 15];14:51-3. Available from: http://www.meajo.org/text.asp?2007/14/2/51/57694

Myasthenia gravis (MG) is a fairly common condition affecting the neuromuscular junction. It is an autoimmune disorder characterized by weakness and fatigability of skeletal muscles. Patients often have ophthalmologic manifestations as the initial complaints, of which ptosis is the most frequent. [1],[2] Ocular MG usually presents with ptosis and/or extraocular muscle imbalance.

The diagnosis of MG is based on the presence of neuromuscular blocking, which is detected by clinical and neurophysiological methods, often combined with provocation tests. Several tests are available to help establish the diagnosis of MG; these include the measurement of serum acetylcholine receptor antibody levels, the rest test, the sleep test, the Tensilon test, electromyography (EMG), and muscle biopsy. [3],[4]

In 1960, Simpson [5] described the effect of temperature in MG. Lowering of the myasthenia muscle temperature by a few degrees leads to a marked improvement in the action of the affected muscles. It is believed that cooling reduces cholinesterase activity, which increases the availability of acetylcholine, and may promote efficiency of acetylcholine in eliciting depolarization at the motor end plate. [2],[6]

In 1979, Saavedra et al [7] described the ice test as an office test for the rapid diagnosis of ptosis caused by MG. Several reports have since postulated that the ice test is a rapid, safe, and inexpensive test for the diagnosis of ocular MG in suspected patients presenting with ptosis. [3],[6],[8],[9],[10],[11]

We investigated the effect of performing the ice test on patients presenting with ptosis and suspected of having MG, and then compared the results to those attained with single-fiber electromyography (SFEMG). To the best of our knowledge, this comparison has not been previously performed.


   Patients and Methods Top


During a 1-year period, 14 (10 females, 4 males) consecutive patients presenting with ptosis and suspected, from their history and clinical examination, of having MG were enrolled in this study. The mean age of the patients included in this study was 38 years (range, 17-56 years), and all had ptosis of at least 2 mm in 1 or both eyes. We excluded patients who had been diagnosed with MG or had previously received medication for MG.

The ice test was performed by placing a surgical glove filled with crushed ice on the ptotic upper lid for 2 minutes. The amount of ptosis was measured before and immediately after the application of ice. A positive response was defined as an improvement of 2 mm or more in the ptotic lid height immediately after removing the ice. If bilateral ptosis was present, the test was performed on the more ptotic lid. Photographs were also taken before and after the ice test to further document the change in lid height.

Patients were then referred to the Department of Neurophysiology for SFEMG testing. First, repetitive supramaximal stimulation of the facial nerve was done. Then simultaneous recording of a pair of single fibers in the frontalis muscle and extensor digitorum muscle was conducted, with the following parameters being recorded: (1) the blocking percentage and (2) jitter or variability in the interpotential interval.


   Results Top


A positive response to the ice test was elicited in 12 (85.7%) of 14 patients [Figure 1]. Of the 2 patients with a negative ice test response, 1 patient was measured as having 1 mm of improvement, whereas the other patient had no detectable change.

All 12 patients with a positive ice test had an abnormal SFEMG finding, consisting of either an abnormal blocking percentage (> 30%) or abnormal jitter (> 45 ΅s). Both patients with a negative ice test had normal SFEMG findings.


   Discussion Top


Myasthenia gravis may have systemic manifestations, ophthalmic manifestations, or both. It may present with only ocular findings and then progress to generalized involvement. The differential diagnosis of ocular myasthenia includes ocular myopathy, muscular dystrophies, myotonic dystrophy, oculopharyngeal dystrophy, Lambert-Eaton myasthenic syndrome, botulism, Miller Fisher syndrome, intracranial lesions, mitochondrial myopathies including chronic progressive external ophthalmoplegia and Kearns-Sayre syndrome, thyroid eye diseases, drug-induced myasthenia, and traumatic and aponeurotic ptosis. [2]

Diagnostic tests for MG include the sleep test, the rest test, the Tensilon test, the acetylcholine receptor antibody assay, muscle biopsy, EMG, and the ice test. However, performing the sleep test in clinical practice is considered impractical. In comparison, the rest test is noninvasive and easy to perform but has a sensitivity of only 50%. The Tensilon test, which can be performed in the office, has a sensitivity of over 90% in generalized MG and over 80% in ocular MG; however, it requires intravenous access and careful monitoring of pulse and blood pressure. Thus, it is time-consuming and has a serious, albeit low, incidence of side effects, especially in elderly and/or cardiac patients. The drawbacks of performing the acetylcholine receptor antibody assay are its expense and its reduced sensitivity (25%-75%) in ocular MG. This assay is also known to produce many false positive results. In contrast, a muscle biopsy is thought to be highly sensitive and specific; however, it is difficult to perform, is available only in a few centers, and is more invasive than other tests. [3]

EMG with repetitive nerve stimulation is widely available. However, it is not very sensitive in ocular myasthenia, and may even be normal in ocular myasthenia or mild generalized MG if unaffected muscles are tested. It is also an invasive test with associated patient discomfort. The most sensitive test is SFEMG, especially in ocular myasthenia where testing of the orbicularis oculi muscle, frontalis muscle, or the superior rectus-levator complex muscle is done. With SFEMG, it is possible to reveal a disturbed neuromuscular function before any transmission block occurs (ie, when other conventional neurophysiological investigations are normal). However, it is also invasive and is available only at certain centers. In addition, it is difficult to perform, is time-consuming, and requires experienced electrophysiologists with specialized equipment. [2],[9]

In 1979, Saavedra et at [7] recommended performing the ice test to diagnose ocular myasthenia. In their study, all 6 patients had an improvement in ptosis after orbital cooling for 5 to10 minutes with an ice pack. Similarly, Sethi et al [8] described the ice test as a new diagnostic test and reported a positive response in 8 of 10 patients with ocular MG.

Ertas et al, [6] who compared the response of ptosis first to the rest test and then to the ice test, reported a greater than 2-mm improvement in ptosis after the ice test in all 12 myasthenia patients. The Tensilon (edrophonium) test was then performed 30 minutes later. Of the 12 patients, 11 had a positive edrophonium test, whereas 1 patient with a positive ice test had a negative response to edrophonium. In a different study, Golnik et al [3] described their ice test findings in 20 myasthenia patients with ptosis. Of the 20 patients, 16 (80%) responded positively to ice testing, even with negative edrophonium or anti-acetylcholine esterase antibody testing. Both Ertas et al [6] and Golnik et al [3] concluded that the ice test is a safe, noninvasive alternative to the edrophonium test.

To the best of our knowledge, a comparison between the ice test and SFEMG testing has not been conducted prior to this study. In contrast to other studies, none of our patients had a previously confirmed diagnosis of MG. When we compared the results of the ice test to those attained with SFEMG, we found that all patients with a positive ice test for ocular MG also had confirmatory findings with SFEMG. Similarly, the 2 patients with a negative ice test also had negative SFEMG testing for MG. We did not perform edrophonium testing or antibody assays for further confirmation of the diagnosis.

In conclusion, we believe that cooling of the ptotic lid with an ice pack for 2 minutes is a safe, inexpensive, and sensitive test for ocular MG diagnosis, which correlates well with SFEMG findings.

 
   References Top

1.Drachman DB. Myasthenia gravis. N Eng J Med 1994;330:1797-1810.  Back to cited text no. 1      
2.Elrod RD, Weinberg DA. Ocular myasthenia gravis. Ophthalmol Clin North Am 2004;17:275-309.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]  
3.Golnik KC, Pena R, Lee AG, Eggenberger ER. An ice test for the diagnosis of myasthenia gravis. Ophthalmology 1999;106:1282-1286.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]  
4.Beekman R, Kuks JB, Oosterhuis HJ. Myasthenia gravis: diagnosis and follow-up of 100 consecutive patients. J Neurol 1997;244:112-118.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]  
5.Simpson JA. Myasthenia gravis: a new hypothesis. Scott Med J 1960;5:419-436.  Back to cited text no. 5      
6.Ertas M, Arac N, Kumral K, Tuncbay T. Ice test as a simple diagnostic aid for myasthenia gravis. Acta Neurol Scand 1994;89:227-229.  Back to cited text no. 6      
7.Saavedra J, Femminini R, Kochen S, deZarate JC. A cold test for myasthenia gravis. Neurology 1979;29:1075.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]  
8.Sethi KD, Rivner MH, Swift TR. Ice pack test for myasthenia gravis. Neurology 1987;37:1383-1385.  Back to cited text no. 8  [PUBMED]  [FULLTEXT]  
9.Kunsell R, Hoffman P. Myopathies and disorders of neuromuscular transmission. In: Miller NR, Newman NJ, eds. Walsh and Hoyt's Clinical Neuro-Ophthalmology. Vol 1. 5th ed. Baltimore, Md: Williams and Wilkins;1998:1406-1431.  Back to cited text no. 9      
10.Kubis KC, Danesh-Meyer HV, Savino PJ, Sergott RC. The ice test versus the rest test in myasthenia gravis. Ophthalmology 2000;107:1995-1998.  Back to cited text no. 10  [PUBMED]  [FULLTEXT]  
11.Ellis FD, Hoyt CS, Ellis FJ, Jeffery AR, Sondhi N. Extraocular muscle responses to orbital cooling (ice test) for ocular myasthenia gravis diagnosis. J AAPOS 2000;4:271-281.  Back to cited text no. 11  [PUBMED]  [FULLTEXT]  


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