text: Abnormal results EMG findings vary with the type of disorder, the duration of the problem, the age of the patient, the degree to which the patient can be cooperative, the type of needle electrode used to study the patient, and sampling error in terms of the number of areas studied within a single muscle and the number of muscles studied overall.  Interpreting EMG findings is usually best done by an individual informed by a focused history and physical examination of the patient, and in conjunction with the results of other relevant diagnostic studies performed including most importantly, nerve conduction studies, but also, where appropriate, imaging studies such as MRI and ultrasound, muscle and nerve biopsy, muscle enzymes, and serologic studies.
  Abnormal results may be caused by the following medical conditions (please note this is not an exhaustive list of conditions that can result in abnormal EMG studies):
  Disorders of Muscle:
  Inflammatory myopathies
  Polymyositis
  Dermatomyositis
  Inclusion body myopathy
  Myotonia Congenita
  Muscular dystrophies:
  Duchenne muscular dystrophy
  Becker muscular dystrophy
  Facioscapulohumeral dystrophy
  Limb girdle muscular dystrophy
  Centronuclear myopathy
  Myotonic dystrophy
  Mitochondrial myopathies
  Disorders of the neuromuscular junction:
  Myasthenia Gravis
  Lambert–Eaton myasthenic syndrome
  Botulism poisoning
  Organophosphate poisoning
  Hypermagnesemia
  Hypocalcemia
  Disorders of Nerves:
  Carpal tunnel syndrome
  Ulnar neuropathy at the elbow
  Radial nerve palsy (Saturday night palsy)
  Peroneal (fibular) nerve palsy
  Diabetic neuropathy
  Alcohol related neuropathy
  Nutritional neuropathy
  Amyloid neuropathy
  AIDP
  CIDP
  Bell's palsy
  Laryngeal neuropathy
  Pudendal neuropathy
  Femoral neuropathy
  Sciatic Neuropathy
  Tibial neuropathy
  Tarsal tunnel syndrome
  Charcot-Marie-Tooth syndrome
  Zoster neuropathy
  Oculomotor, Facial, vagal, trigeminal, glossopharyngeal, spinal accessory neuropathies
  Hemifacial spasm
  Multifocal motor neuropathy
  Axillary neuropathy
  Long thoracic neuropathy
  Suprascapular neuropathy
  Toxic neuropathies
  Drug-induced neuropathies
  Complex Regional Pain Syndrome (CRPS)
  Plexus disorders:
  Neuralgic Amyotrophy (idiopathic brachial plexitis)
  Traumatic brachial plexopathy
  Lumbosacral radiculopathy
  Hirayama disease
  Root disorders:
  Cervical, thoracic, lumbar, sacral radiculopathy
  Spinal stenosis
  Arachnoiditis
  Leptomeningeal disorders
  Motor neuron disease
  Amyotrophic lateral sclerosis
  West Nile virus
  Poliomyelitis
  Kennedy's syndrome (Spinobulbar muscular atrophy).