Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 51, Num. 2, 2003, pp. 283-285

Neurology India, Vol. 51, No. 2, April-June, 2003, pp. 283-285

Letter to Editor

Management of ocular myasthenia gravis coexisting with thyroid ophthalmopathy

S. Kumar
Neurology Unit, Department of Neurological Sciences, Christian Medical College Hospital, Vellore, Tamilnadu-632004, India.
E-mail: drsudhirkumar@yahoo.com

Code Number: ni03092

Sir,

I read with interest the recent article by Yaman A et al.¹ They have described their experience of managing a case of ocular myasthenia gravis in association with thyroid ophthalmopathy. However, I would like to make certain observations.

Firstly, they have performed thymectomy for ocular myasthenia. Patients with ocular myasthenia have been noted to have poor prognosis after thymectomy.² Therefore, thymectomy is not recommended for patients with myasthenia gravis who belong to Ossermann Class I (ocular symptoms alone).³ In the present case, if there was a suspicion of malignant thymoma, though unlikely, a biopsy could have been performed and thymectomy avoided. Also, the patient in this case received two sessions of plasmapheresis. There was no clear indication for the same. She had ocular symptoms alone that had responded well to medical therapy with pyridostigmine. There are specific indications of plasmapheresis in the treatment of myasthenia gravis- namely myasthenic crisis, chronic myasthenic patients who fail to respond adequately to conventional medical therapy and preoperatively in patients with poorly controlled disease.³

They conclude in their paper that ptosis is an unexpected symptom in thyroid ophthalmopathy. However, in an earlier report,⁴ 60% of patients (six out of ten studied) with thyroid ophthalmopathy were found to have ptosis. In two of them, the ptosis was fluctuating in nature too. Interestingly, fluctuating ptosis, in addition to myasthenia gravis and thyroid ophthalmopathy, may also be found in mitochondrial myopathies and ptosis secondary to intracranial pathology such as dorsal midbrain glioma.⁵ Ptosis in thyroid ophthalmopathy may be a `pseudoptosis' secondary to eyelid retraction in the other eye or in some cases, it may be true ptosis.⁴

In conclusion, plasmapheresis and thymectomy are not recommended for ocular myasthenia, which otherwise responds well to medical therapy with pyridostigmine. Ptosis may occur in cases of thyroid ophthalmopathy without associated ocular myasthenia.

REFERENCES

1. Yaman A, Yaman H. Ocular myasthenia gravis coincident with thyroid ophthalmopathy. Neurol India 2003;51:100-1.
2. Tellez-Zenteno JF, Remes-Troche JM, Garcia-Ramos G, Estanol B, Garduno-Espinoza J. Prognostic factors of thymectomy in patients with myasthenia gravis: a cohort of 132 patients. Eur Neurol 2001;46:171-7.
3. Sanders DB, Scoppetta C. The treatment of patients with myasthenia gravis. Neurol Clin 1994;12:343-68.
4. Batocchi AP, Evoli A, Majolini L, Lo Monaco M, Padua L, Ricci E, et al. Ocular palsies in the absence of other neurological or ocular symptoms: analysis of 105 cases. J Neurol 1997;244:639-45.
5. Ragge NK and Hoyt WF. Midbrain myasthenia: fatigable ptosis, `lid twitch' sign, and ophthalmoparesis from a dorsal midbrain glioma. Neurology 1992;42:917-9.

Authors' Reply

A. Yaman, H. Yaman*
Süleyman Demirel University, Medical School, Department of Neurology, 0sparta, Turkey;* Akdeniz University, Medical School, Department of Family Medicine, Antalya, Turkey.
E-mail: hakanyaman@akdeniz.edu.tr

Sir,

We thank for the contribution and comments of the author of the letter written in response to our article "Ocular myasthenia gravis coincident with thyroid ophthalmopathy".¹ We would like to make some clarifications concerning the points he/she argues. Firstly, it should be emphasized that, a widespread consensus about the place and long term effects of thymectomy in the treatment of myasthenia gravis, especially in the ocular form, still does not exist; since there is lack of randomised, controlled studies. Although generally thymectomy is not recommended for patients with purely ocular myasthenia, dramatic improvement after thymectomy in several such patients has been observed. So, using this treatment in ocular myasthenia may be considered in certain circumstances, particularly in young patients with relatively recent onset of myasthenia to reduce the possibility that the disease will become generalised and ultimately require long term medications.^2-4 Moreover, our patient had a suspected thymic mass and a high acetylcholine receptor antibody titer which may be accepted as other indications for thymectomy.³

Besides other indications, plasmapheresis is indicated and used as an adjuvant therapy in the preparation of myasthenic patients for thymectomy regardless of the stage and type of the disease, although being more important and beneficial for the severe forms. It has been shown that it reduced the post-operative myasthenic complications, length of hospital stay and cost.⁵

The author states that ptosis is a frequently encountered symptom during the course of thyroid ophthalmopathy citing a study conducted in a very limited number of patients (six out of ten). However, generally accepted knowledge does not confirm this statement. Ptosis in thyroid ophthalmopathy is rare,⁶ and should alert the physician to the possibility of myasthenia gravis.⁷ Furthermore, besides clinical signs, a high acetylcholine receptor titer and a positive response to neostigmine test were present in our patient, confirming the diagnosis of myasthenia gravis.¹

REFERENCES

1. Yaman A, Yaman H. Ocular myasthenia gravis coincident with thyroid ophthalmopathy. Neurol India 2003;51:100-101.
2. Sanders DB, Howard JF. Disorders of Neuromuscular Transmission.In: Bradley WG, Daroff RB, Fenichel GM, Marsden CD, editors. Neurology in Clinical Practice. 3rd edn. Boston: Butterworth-Heinemann; 2000. Vol II. pp.2167-85.
3. Lucchi M, Mussi A, Ricciardi R, Angeletti CA. Thymectomy in ocular myasthenia gravis (letter). J Thorac Cardiovasc Surg 2003;125:740-1.
4. Nieto IP, Robledo JP, Pajuelo MC, Montes JA, Giron JG, Alonso JG, Sancho LG. Prognostic factors for myasthenia gravis treated by thymectomy: Review of 61 cases. Ann Thorac Surg 1999;67:1568-71.
5. Seggia JC, Abrev P, Takatani M. Plasmapheresis as preparatory method for thymectomy in myasthenia gravis. Arq Neuropsiquiatr 1995;53:411-5.
6. Glaser JS. Neuro-ophthalmologic examination: General considerations and special techniques. In: Glaser JS, editor. Neuro-ophthalmology. 2nd edn. Philadelphia: JB Lippincott Company; 1990. pp. 37-60.
7. Shaw PJ. Thyroid Disease and the Nervous System. In: Aminoff MJ, editor. Neurology and General Medicine. 3rd edn. New York: Churchill Livingstone; 2001. pp. 317-39.

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