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Show Journal of Neuro- Ophthalmology 20( 4): 291- 294, 2000. © 2000 Lippincott Williams & Wilkins, Inc., Philadelphia Letters to the Editor To the Editor: The authors thank Kaminski et al. for commenting on our paper ( 1). They raise an important concern- did this patient actually have myasthenia gravis ( MG)? We too initially had a concern over the diagnosis. The initial findings did not include ptosis but only a subtle, fleeting gaze incomitancy and atypical accommodative findings. The abnormal accommodative findings were similar to those previously reported in another paper in which traditional tests confirmed the diagnosis of MG ( 2). The consulting neurologist thought that it would be prudent to obtain a visual evoked potential ( VEP) to rule out demyelinating disease, even at this late stage. Our patient refused a Tensilon ( Zeneca Pharmaceuticals, Wilmington, DE), and single- fiber electromyogram ( EMG). In this era of informed consent and the Internet, the patient's rights must be respected. Evaluation of circulating acetylcholine receptor antibodies, thyroid ( T3, T4, thyroid- stimulating hormone [ TSH]), and of the thymus were made ( computed axial tomography [ CAT] scan). Though not previously mentioned, because we considered these tests part of comprehensive neurologic examination to rule out MG, they were negative. In addition, we considered and ruled out chronic progressive external ophthalmoplegia, internuclear ophthalmoplegia, diabetes, intracranial lesions, and Lambert- Eaton syndrome ( 3,4). The diagnosis of myasthenia was not made on the basis of the accommodative findings, but rather on the basis of the fatigability of the extraocular muscle system: ptosis, phoria, and fusional amplitudes- all of which showed measurements of progressive fatigue from morning to night over a period of months with a positive response to Mestinon ( see Figs. 1 & 2) ( 1). The phoria and fusional amplitudes were accurately and objectively measured with cover test and prism bar while the examiner observed the position of the eyes. Tensilon and Mestinon are both anticholenesterases with similar response characteristics except duration. A successful clinical trial of Mestinon is clinically equivalent to a Tensilon test ( 5). Kaminski, Daroff, and Dell'Osso also raise the issue that Mestinon ( Tensilon) is not specific for MG while maintaining that other tests such as the ice test are both sensitive and very specific, which they reference ( 6). Daroff, in another paper ( 7), stated that a " positive test ( Tensilon) is virtually diagnostic of myasthenia gravis." The ice test study referenced has experimental errors and thus should be interpreted cautiously. First, the investigators did not differentiate ocular from systemic MG; second, it appears probable that the experimenter evaluated all patients before and after the ice test and, thus, knew the status of the patients before testing; third, measurement reliability was never established, nor the effect of restraining the frontalis muscle; and lastly, the effect of the duration of MG is unknown. With this in mind, " a positive ice test was noted in 16 of 20 ( 80%)," with one patient getting worse. A reliable adjunct, the ice test is not diagnostic, as implied by Kaminski, Daroff, and Dell'Osso. The finding of muscarinic sites in MG reinforces our findings by providing the physiologic mechanism for accommodative involvement. As pointed out in the introduction of our paper, Manson and Stern reported that, after the injection of Tensilon, the accommodative amplitude was unaffected in normals but increased in half of the patients with MG. Thus, a positive Tensilon ( Mestinon) response to accommodation is strongly suggestive of a diagnosis of MG. One of our intents was to make clinicians and researchers aware that specific and subtle abnormal accommodative findings ( as well as vergence) may be the first sign of MG in the prepresbyopic population. Hence, measurements of accommodative facility might provide useful diagnostic information. Furthermore, a simple treatment such as appropriate spectacle correction to decrease both the accommodative and vergence demand may be very helpful in certain patients with MG. Finally, we hope that we might stimulate clinician( s) to evaluate accommodative facility in a larger sample of prepresbyopic MGs and determine how common these findings are. Thank you for allowing us to address Kaminski et al.' s concerns Jeffrey Cooper, MS, OD Gayle J. Pollak, OD Kenneth J. Ciuffreda, OD, PhD Philip Kruger, OD, PhD Jerome Feldman, PhD State College of Optometry State University of New York New York, New York REFERENCES 1. Cooper J, Pollack GJ, Ciuffreda KJ, et al. Accommodative and vergence findings in ocular myasthenia: a case analysis. J Neu-roophthalmol 2000; 20: 5- 11. 2. Cooper J, Kruger P, Panariello G. The pathognomonic pattern of accommodative fatigue in myasthenia gravis. Bino Vis 1988; 3: 141- 8. 3. Moorthy G, Behrens MM, Drachman DB, et al. Ocular pseudo-myasthenia or ocular myasthenia " plus": a warning to clinicians. Neurology 1989; 39: 1150- 4. 4. Leigh JR, Zee DS. Chapter 9: Diagnosis of peripheral ocular motor palsies and strabismus. In: The Neurology of Eye Movements ( ed 2). Philadelphia: FA Davis, 1991. 5. Sergott RC. Ocular myasthenia. In: Lisak RP, ed. Handbook of Myasthenia Gravis and Myasthenic Syndromes. New York: Marcel Dekker, 1994. 6. Golnik KC, Pena R, Lee AG, Eggenberger ER. An ice test for the diagnosis of myasthenia gravis. Ophthalmology 1999; 106: 1282- 6. 7. Daroff RB. The office Tensilon test for ocular myasthenia gravis. Arch Neurol 1986; 43: 843- 4. 291 292 LETTERS TO THE EDITOR To The Editor: Cooper et al. ( 1), after reviewing the contradictory literature on the effects of myasthenia gravis ( MG) on accommodation, presented a patient with accommodative insufficiency allegedly secondary to MG. Unfortunately, they did not establish that their patient had MG. The patient had ptosis that did not fatigue and did not improve with the sleep test or ice test ( a sensitive and very specific test for partial ptosis in MG [ 2]). The authors did not perform the other very basic, routine tests to diagnose MG, such as Tensilon ( Zeneca Pharmaceuticals, Wilmington, DE), which is safe in asthmatics pre-treated with atropine, repetitive nerve stimulation, single- fiber electromyogram ( EMG), or a determination of circulating acetylcholine receptor antibodies. Obtaining a visual evoked potential after the patient developed ptosis suggests neurologic naivety. The previous patient reported by these authors ( 3) did have a positive Tensilon test and a single- fiber EMG said to be confirmatory of MG. The only diagnostic support they had for MG was " improvement" ( although undocumented with photographs) of the ptosis with Mestinon ( Zeneca). However, improvement with an anticholinesterase medication is not specific for MG but occurs in other neuromuscular conditions ( 4). Moreover, Mestinon affects muscarinic synapses in smooth muscle ( 5). Thus, alterations of accommodation after Mestinon do not establish a diagnosis of MG. Michaelson et al. ( 6) reported antimuscarinic acetylcholine receptor antibodies in MG, but there is no clinical or physiologic evidence to suggest that these are of pathogenic significance ( 7). Although unrelated to the main point of the Cooper et al. report and our letter, the basis for the preferential involvement of the extraocular muscles in MG is more complex than stated ( for review, see Kaminski and Ruff [ 8], and Kaminski [ 9]). Henry J. Kaminski, MD Robert B. Daroff, MD Louis F. DelPOsso, PhD Cleveland, Ohio REFERENCES 1. Cooper J, Pollack GJ, Ciuffreda KJ, et al. Accommodative and vergence findings in ocular myasthenia: a case analysis. J Neu-roophthalmol 2000; 20: 5- 11. 2. Golnik KC, Pena R, Lee AG, et al. An ice test for the diagnosis of myasthenia gravis. Ophthalmology 1999; 106: 1282- 6. 3. Cooper J, Kruger P, Panariello G. The pathognomonic pattern of accommodative fatigue in myasthenia gravis. Bino Vis 1988; 3: 141- 8. 4. Moorthy G, Behrens MM, Drachman DB, et al. Ocular pseudo-myasthenia or ocular myasthenia " plus": a warning to clinicians. Neurology 1989; 39: 1150- 4. 5. Argov Z, Wirgun I. Drugs and the neuromuscular junction: Pharmacotherapy of transmission disorders and drug- induced myasthenia syndromes. In: Lisak RP, ed. Handbook of myasthenia gravis and myasthenic syndromes. New York: Marcel Dekker, Inc., 1994: 295- 340. 6. Michaelson D, Cooper J, Lindstrom J. Antibodies to muscarinic acetylcholine receptors in myasthenia gravis. Biochem Biophys Res Commun 1982; 104: 52- 7. 7. Lennon V. Serologic profile of myasthenia gravis and distinction from Lambert- Eaton myasthenic syndrome. Neurology 1997; 48 ( Suppl 5): S23- 7. 8. Kaminski H, Ruff R. Ocular muscle involvement by myasthenia gravis. Ann Neurol 1997; 41: 419- 20. 9. Kaminski H. Acetylcholine receptor epitopes in ocular myasthenia. Ann NY Acad Sci 1998; 841: 309- 20. To the Editor: We make the following brief points related to the Response by Cooper et al.: 1. Fatigability is only suggestive, but certainly not diagnostic, of myasthenia. 2. A clinical trial of Mestinon is not equivalent to a Tensilon test, nor did Sergott make that statement in his chapter ( 1). Thus, Daroff s statement that a positive Tensilon test " is virtually diagnostic of myasthenia gravis" ( 2) is irrelevant in this context. Moreover, Daroff was referring to a positive Tensilon test properly interpreted, meaning resolution of eyelid ptosis, or the direct observation of the strengthening of an extraocular muscle, and not indirect measures, such as lessening of a phoria. The major point of Daroff s paper was that a cover test, prism bar, red glass, Mad-dox rod, and other techniques, may give spurious responses to Tensilon testing, and direct observation is essential ( 2). 3. The authors did not establish the diagnosis of myasthenia gravis in their reported patient ( 3). Henry J. Kaminski, MD Robert B. Daroff, MD Louis F. Dell'Osso, PhD Cleveland, Ohio REFERENCES 1. Sergott RC. Ocular myasthenia. In: Lisak RP, ed. Handbook of myasthenia gravis and myasthenic syndromes. New York: Marcel Dekker, 1994: 21. 2. Daroff RB. The office Tensilon test for ocular myasthenia gravis. Arch Neurol 1986; 43: 843^ 4. 3. Cooper J, Pollack GJ, Ciuffreda KJ, et al. Accommodative and vergence findings in ocular myasthenia: a case analysis. J Neu-roophthalmol 2000; 20: 5- 11. To the Editor: Kim and Kosmorsky described a fascinating case that they called an arteriovenous malformation but incorrectly titled the paper Arteriovenous Communication in the Orbit. I believe that the referring ophthalmologist made the correct diagnosis- that this case represented a dural cavernous fistula with retrograde orbital filling. The setting of symptoms after coronary artery bypass surgery is the perfect setting for dural fistulization. The proximal branches from the ophthalmus, labeled " F," appear to at least be in the anterior portion of the cavernous sinus. It J Neuro- Ophthalmol, Vol. 20, No. 4, 2000 LETTERS TO THE EDITOR 293 is not surprising that other muscular branches contributed to the fistula. The argument as to whether all dural fistulas represent arteriovenous malformation or are a result of the dynamic effect of partial venous thrombosis may remain controversial. The age of the patient suggests that this disease is acquired. The most important films, showing selective right external carotid angiography that demonstrates the internal maxillary artery filling the superior ophthalmic vein and retrograde filling presumably of cavernous sinus, appear to make this case a dural fistula of the most anterior aspect of the cavernous sinus. Norman J. Schatz, MD Coral Gables, Florida To the Editor, Once again the keen eye of Dr. Schatz strikes at the heart of an issue. In our case report, we termed the lesion an arteriovenous malformation in a feeble attempt to gussy up the title of the paper. After reviewing the chart, we discovered that the lesion was termed an orbital du-ral- based fistula. The exact point of origin of this lesion cannot be determined precisely, but I would concede that an anterior cavernous sinus location is possible. Dr. Schatz also correctly notes that there is controversy in the terminology applied to these lesions; some pathologists would argue that a dural fistula is a type of arteriovenous malformation. Like Ivan Ivanovich, the great Russian wrestler, discovered, you can't win them all. Thank you, Dr. Schatz, for once again demonstrating that the oldest dogs can still do the neatest tricks. Gregory S. Kosmorsky, DO Cuyahoga Falls, Ohio To the Editor: I want to present a brief summary of a patient's case in hope that it might elicit information about similar cases from readers. A 50- year- old previously healthy woman developed binocular diplopia in her 20s. Further details are not available except that a cause could not be found, even after an extensive in- patient evaluation. She had several unsuccessful strabismus procedures. While in her early 40s, the diplopia worsened, and she began to have pain in her orbits precipitated by exertion or eye movements. She also complained that her eyes became red v/ hen she exerted herself. When this patient was evaluated for limb muscle pain precipitated by exertion, easy fatigue, and weakness, she was found to have McArdle disease. Her daughter, who has not been tested, has had some nonocular symptoms. The patient's visual function is entirely normal, and she is emmetropic. Her upper lids look puffy, similar to the appearance of the lids in those with Graves ophthalmopathy. There is no lid retraction, ptosis, or lag. Ex-ophthalmometry readings are 21 mm bilaterally, and the orbits are slightly tight. There is some injection of the bulbar conjunctiva of both eyes. Her pupils are unremarkable. The only defect in her eye movements that I have found is a right hypertropia, worse on right gaze with left inferior oblique under action. There is no torsional diplopia, and head tilt does not alter the hypertropia. Her eye movements appear to have a normal velocity. There are no fundus abnormalities. When I first examined her, I thought she might have the orbitopathy of Graves disease, but scans of her orbits do not show enlargement of muscles, or anything else for that matter! Findings from thyroid function tests were normal. Have any readers encountered patients with eye muscle involvement in McArdle disease? Simmons Lessell, MD Boston, Massachusetts Caution During Performance of the Red- Green Glasses Test for Functional Visual Loss To the Editor: The red- green glasses test for detection of functional visual loss is performed by placement of the green filter in front of the eye with alleged visual loss and placement of the red filter in front of the eye with normal sight. Small red letters on a white sheet of paper are written lightly with a red pencil or a felt- tip pen. When performed correctly, the patient, who believes he or she is reading binocularly, will actually only be reading from the eye behind the green filter. Therefore, near vision in the eye with alleged visual loss may be objectively measured. If the examiner presses too firmly when writing the red letters, however, an impression on the paper is created that may allow the patient to see the letters through either filter. The examiner should test ( preferably not in the patient's view) whether the red letters are written sufficiently lightly so that they cannot be seen through the red filter. When performing this test, it is critical that the examiner place his or her own near correction, in addition to the red- green glasses. Although red letters through a red filter may not be apparent without correction, they may be visible when appropriate correction is placed. With my own near correction in place, I am surprised to see how lightly I must write with red pencil to prevent sight through the red filter. The above proviso may avoid false- positive red-green glass test results and erroneous diagnoses of functional visual loss, especially in children. Michael L. Slavin, MD Long Island Jewish Medical Center Albert Einstein College of Medicine Great Neck, New York J Neuro- Ophthalmol, Vol. 20, No. 4, 2000 1 294 LETTERS TO To the Editor: I read with interest the article by Sadda et al. ( 1) that describes the case of a patient with anomalous optic disc elevation. The authors found ultrasonographic evidence of increased subarachnoid fluid around the optic nerve, despite normal intracranial pressure results. Stimulated by similar findings in two patients, we have studied the meninges of the optic nerve in humans and have found a dense system of lymphatic capillaries in the dura of the optic nerve that probably represent a functional cerebrospinal fluid pressure regulating system. Labeling experiments indicate drainage of cerebrospinal fluid from the subarachnoid space of the optic nerve into the lymphatic capillaries in the dura. Until now, the concept of a homogenous pressure in the entire cerebrospinal fluid compartment, including ventricles, subarachnoid space, and cysteras, has not been challenged. This concept, however, is based on hypothesis rather than on reliable measurements, which are notoriously difficult in compartments with small volumes. Sadda et al. ( 1) carefully avoided the term papilledema in their paper. This may be justified according to current terminology because they did not find an elevated intracranial pressure in their patient. Based on the histologic findings described in our paper ( 2), and because the pressure in the different cerebrospinal fluid compartments may not necessarily be homogenous, I believe that their case might have been papilledema as a result of a local increase of the cerebrospinal fluid pressure that caused an optic nerve sheet tight compartment syndrome with elevated pressure in the subarachnoid space of the affected optic nerve. H. Esriel Killer, PD Dr. med Augenklinik, Kantonsspital Aarau, Switzerland REFERENCES 1. Sadda SR, DiBernardo C, Roub RN, et al. Anomalous optic disc elevation associated with ultrasonographic evidence of increased subarachnoid fluid. J Neuwophthalmol 2000; 20: 25- 7. 2. Killer HE, Laeng RL, Groscurth P. Lymphatic capillaries in the meniges of the human optic nerve. J Neuroophthalmology 1999; 19: 222- 8. Authors' Reply To the Editor: Dr. Killer raises the question of whether the bilateral optic disc elevation in our patient ( 1), which we believe was congenital anomalous elevation, was actually local- THE EDITOR ized papilledema, i. e., focal increased intracranial pressure related to abnormal regulation of cerebrospinal fluid drainage by the lymphatic drainage system in the meninges of the optic nerve, which Killer et al. ( 2) described in 1999. He postulates that this could account for the increased fluid detected by ultrasonography around the orbital portion of the optic nerves on three occasions in our patient, who never had evidence of increased intracranial pressure as tested by lumbar puncture. We do not believe that this is the case, for several reasons. First, this patient's optic disc elevation had been present for at least 20 years and was documented photographically over 10 years. If this were true disc swelling ( localized papilledema), we would have expected some changes in the appearance of one or both nerves to occur over this period of time, particularly the development of optic disc pallor and peripapillary retinal nerve fiber layer defects, just as one would expect to see in a patient with untreated increased intracranial pressure or untreated focal compression of the optic nerve from an orbital mass. In addition, we would have expected the patient to have experienced some evidence of visual sensory dysfunction during this time. Therefore, although Dr. Killer's speculations are intriguing, we do not believe they are correct. Of course, the best way to determine this would be to measure the cerebrospinal fluid pressure in the nerve sheath directly, as described by Liu and Michon ( 3) in 1995; however, these measurements were performed only in patients scheduled for enucleation or evisceration and would undoubtedly place our patient's vision at some risk. Alternatively, we could measure visual evoked potentials in our patient; this might be a more sensitive indicator of compression of the nerve than our clinical assessment. In the meantime, we believe that it is most likely that the fluid that surrounds the optic nerves in our patient is the result of anomalous patulous optic nerve sheaths and does not represent trapped cerebrospinal fluid under pressure. Srinivas R. Sadda, MD Cathy Dibernardo, RN Neil R. Miller, MD Johns Hopkins Hospital Baltimore, Maryland REFERENCES 1. Sadda SR, DiBernardo C, Roub RN, et al. Anomalous optic disc elevation associated with ultrasonographic evidence of increased subarachnoid fluid. J Neuwophthalmol 2000: 20: 25- 7. 2. Killer HE, Laeng HR, Croscurth P. Lymphatic capillaries in the meninges of the human optic nerve. J Neuroophthalmol 1999; 19: 222- 8. 3. Liu D, Michon J. Measurement of the subarachnoid pressure in the optic nerve of human subjects. Am J Ophthalmol 1995; 119: 81- 5. 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