Muscular Disorders
                          ==================


þ Myasthenia Gravis
 - Ice Test: 
   An alternative to edrophonium testing is the ice-test, as described here. It 
   is most useful in patients with ptosis. Both edrophonium and the ice-test are 
   less useful in patients who present with limb weakness only due to the diffi 
   culty in quantifying any response. Cooling improves muscarinic neuromuscular 
   transmission, possibly by decreasing the activity of acetylcholinesterase, 
   and this explains the resolution of ptosis in patients with myasthenia 
   gravis. For appropriately selected patients, the test is approximately 
   80% sensitive for myasthenia gravis – this is comparable to the sensitivity 
   of the Tensilon test and actually exceeds the sensitivity of testing for 
   antiacetylcholine receptor antibodies for ocular myasthenia gravis. The 
   specificity is not known, although it is reported that patients with ptosis 
   not related to myasthenia gravis do not improve with the ice-test.
 - This involved holding ice packs over the patient’s closed eyes for 1 min and 
   monitoring for resolution of ptosis.
   [Browning, J., M. Wallace, et al. (2011). "Bedside testing for myasthenia 
   gravis: the ice-test." Emerg Med J 28(8): 709-711.]
   Summary A 67-year-old man presented to the acute medical take with a history 
   of droopy eyelids and difficulty swallowing. A diagnosis of myasthenia gravis 
   was suspected from the clinical history. The patient's symptoms were 
   progressive, raising concerns of aspiration pneumonia or respiratory 
   compromise if untreated. Definitive diagnosis of myasthenia gravis relies 
   upon a combination of serological and electrophysiological investigations, 
   the results of which are not immediately available in an acute situation. 
   Bedside tests are therefore of practical clinical importance to enable prompt 
   and effective initiation of treatment, particularly where critical symptoms 
   are present. The ice-test is a straightforward and non-invasive investigation 
   with a high sensitivity for myasthenia gravis and is a useful alternative to 
   edrophonium testing. It is especially helpful in patients with cardiac and 
   respiratory co-morbidities for whom acetylcholinesterase inhibitors are 
   contraindicated. We describe a case where this simple bedside test 
   successfully expedited the correct treatment and improved patient care.]
 - Aminoglycosides are notorious for causing increased weakness in
   patients with myasthenia gravis.
   Reference: Tintinalli 3rd ed. p 824
 - Tensilon (Edrophonium) test.
   Used to diagnose, and in mild crises, to see if is a myasthenic crisis or
   an overtreatment (cholinergic) crisis:
  + draw up 10 mg (1cc)
  + give 0.2 cc (2 mg); if no response in 45 seconds give the rest
   If patient improves, needs more treatment with Mestinon.
 - Mestinon (pyridostigmine):
  + usual dose 30 mg
  + IV is dangerous, but IM dose is 1/30 of PO dose (e.g., 1 mg)