The Tensilon Test: A Case Report - Gundersen Health System

Author:
Balaji Vishwanat, MD
Physician Emeritus,
Department of Neurology
Gundersen Lutheran Health System
La Crosse, Wisconsin
Address for correspondence:
David Hartman, PhD,
BC-ANCDS(A)
Mail Stop EB3-002
Gundersen Lutheran Health System
1900 South Avenue
La Crosse, WI 54601
Telephone: (608) 775-9000
Fax: (608) 775-6358
email: dehartma@gundluth.org
The Tensilon Test: A Case Report
Abstract
A patient presented with symptoms and signs consistent with a diagnosis of myasthenia
gravis (MG), a neuromuscular junction disorder. Herein, findings from the patient’s physical
examination and results of the edrophonium chloride (Tensilon) test administered to confirm
the MG diagnosis are reported. The symptoms and underlying pathophysiology of MG are
described. Finally the array of tests that can be used to aid in a diagnosis of MG are reviewed.
A
68-year-old man presented with a 2-month history of
weakness of his jaw, drooping of his left upper eyelid, and
double vision. All his symptoms were intermittent in nature. His
jaw tired after he had chewed 3 or 4 mouthfuls and would recover
after resting for a couple of minutes. The left upper eyelid would
be fine in the morning but would start drooping by noon and stay
that way the rest of the day. The double vision was also prominent
toward the end of the day. He had experienced no difficulty
swallowing or breathing. He had experienced no weakness of his
neck muscles. His extremities were perfectly strong. Medical history
was significant for rheumatic fever in childhood leading to aortic
stenosis. He required aortic valve replacement and 2 revisions.
Complete review of systems was unremarkable. The patient was
taking no prescription medications.
Findings from a general physical examination were
unremarkable. A very definite ptosis was present on the left. The
patient had binocular diplopia on right and left lateral gaze. Jaw
muscles were normal but easily fatigued. Mild bilateral lower motor
neuron facial weakness was evident. Limb musculature strength
was normal. Deep tendon reflexes were normal and the plantar
responses flexor. There were no sensory deficits.
An edrophonium chloride (Tensilon) test was performed
(Figures 1 and 2).
(1) What is the likely diagnosis?
(2) What does the Tensilon test show?
(3) How would you manage this patient?
junction by antibodies to the postsynaptic acetylcholine receptors
(AChR). Normal quanta of acetylcholine are released at the
nerve terminal, but the response is reduced, leading to weakness.
In contrast, the defect in Lambert-Eaton syndrome lies in the
presynaptic nerve terminals due to antibodies directed toward
calcium channels and the release of insufficient quanta of
acetylcholine. 1 Cobra venom and bungarotoxin produce blockage
of neuromuscular transmission by prolonged nondepolarization of
the neuromuscular junction. Botulinum toxin causes blockage of
acetylcholine release from nerve terminals.
In MG, the extraocular, facial, jaw, bulbar, neck, and shoulder
girdle muscles are affected, most commonly in that order. The
extremity and respiratory muscles are also often involved. The
muscle weakness typically fluctuates, being minimal in the
DISCUSSION
This gentleman presented with classical symptoms and signs
of myasthenia gravis (MG). MG is the prototypic neuromuscular
junction disorder. Other entities in this spectrum are Lambert-
Eaton myasthenic syndrome, botulism, congenital MG, familial
infantile MG, and envenomation by cobra or alpha-bungarotoxin.
A transitory form of MG affects 10% to 20% of the newborns
whose mothers have autoimmune MG.
The underlying pathophysiology in MG is distortion and
simplification of the end-plate membrane in the neuromuscular
Figure 1. Ptosis of the left upper
and right lower lid is evident.
Figure 2. Following injection of
the edrophonium chloride, the
ptosis is resolved. The frontal
and nasolabial creases are more
prominent due to improved tone
in the facial muscles.
Gundersen Lutheran Medical Journal • Volume 5, Number 1, July 2008 19

morning and getting more noticeable toward the end of the day.
Since MG is an autoimmune disease, patients tend to have an
increased incidence of other disorders, such as rheumatoid arthritis,
Hashimoto thyroiditis, and pernicious anemia.
The Tensilon test can be very useful in the bedside diagnosis
of MG. Ideally the test should be done in a double-blind fashion
to improve objectivity. Edrophonium chloride is a short-acting
cholinesterase inhibitor and will rapidly improve neuromuscular
deficits due to MG. Ten mg of the drug in 1- cc doses are
administered intravenously over about a minute. It is important
that readily observable deficits are present so that any improvement
that occurs is appreciated. The effect lasts about 5 minutes. The
usual side effects are lacrymation, sweating, abdominal cramps,
bradycardia, and occasionally hypotension, all resolving within
5 minutes. The author dilutes 1 cc of the drug with 1 cc of the
patient’s blood and administers a 2-mg test dose. If there are no
adverse effects, the remainder of the drug is given over the next
minute. Electrocardiographic monitoring is not necessary.
Another rapid and easy test for MG involves applying ice to
the ptotic eyelid for a few minutes. Cooling maintains the sodium
channels open for a longer period, thus enhancing the action
potentials at the neuromuscular junction. This is the underlying
principle that aggravates the symptoms of myotonia. The converse
of this is also the reason for aggravation of symptoms in multiple
sclerosis when the body temperature rises above normal.
Laboratory tests can aid in diagnosis. Antibodies against AChR
are found in most patients with MG. Antistriational antibodies are
also found in patients who have thymic hyperplasia or thymoma.
The antibody titers, however, do not correlate with the severity of
the clinical illness.
A small subset of patients with MG do not have AChR
antibodies but may have antibodies to muscle-specific tyrosine
kinase (MuSK). These patients tend to have more prominent
bulbar and respiratory muscle involvement and do not respond
well to cholinesterase inhibitors. 2
Since there is high incidence of thymic hyperplasia and of
benign or malignant thymoma in patients with autoimmune MG,
a computed tomographic (CT) scan of the chest should be obtained
on all patients. Our patient’s CT scan revealed a thymoma.
Repetitive nerve stimulation studies and single-fiber
electromyography can also aid in diagnosis of MG.
The immediate treatment of MG consists of an oral
anticholinesterase-inhibiting drug such as pyridostigmine
bromide. 3 The use of immunosuppressive drugs such as
corticosteroids, azathioprine, cyclophosphamide, cyclosporin,
mycophenolate mofetil, and rituximab may be necessary in some
patients. Myasthenic crises usually respond well to plasmapheresis
or intravenous immunoglobulin therapy. Thymectomy is
indicated for thymoma and should be considered in all patients
not responding to conventional medical therapies.
Drugs known to cause neuromuscular blockage should be
avoided. Other drugs that have a potential for aggravating the
symptoms of MG include quinine, quinidine, procainamide,
aminoglycosides, beta blockers, and calcium channel blockers.
Induction of autoimmune MG by D-penicillamine 4 and statins 5
is well documented.
REFERENCES
1. O’Neill JH, Murray NM, Newsom-Davis J. The Lambert-Eaton myasthenic
syndrome. A review of 50 cases. Brain. 1988;111(Pt 3):577-596.
2. Sanders DB, El-Salem K, Massey JM, McConville J, Vincent A. Clinical aspects of
MuSK antibody positive seronegative MG. Neurology. 2003;60(12):1978-1980.
3. Keesey JC. Clinical evaluation and management of myasthenia gravis. Muscle
Nerve. 2004;29(4):484-505.
4. Albers JW, Hodach RJ, Kimmel DW, Treacy WL. Penicillamine-associated
myasthenia gravis. Neurology. 1980;30(11):1246-1249.
5. Purvin V, Kawasaki A, Smith KH, Kesler A. Statin-associated myasthenia gravis:
report of 4 cases and review of the literature. Medicine. 2006;85(2):82-85.
Pelican
Photograph by David E. Hartman, PhD
Gundersen Lutheran
20 Gundersen Lutheran Medical Journal • Volume 5, Number 1, July 2008