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Introduction When EMG studies are performed for evaluation of suspected ALS, the El Escorial diagnostic criteria require fibrillation potentials to serve as evidence of lower motor neuron disease. The Awaji Criteria allow fasciculation potentials together with neurogenic motor unit potentials to serve as EMG evidence of lower motor neuron disease. Although the Awaji Criteria have been considered to facilitate the diagnosis of ALS by not requiring fibrillation potentials on EMG, the El Escorial Criteria for the diagnosis of ALS continue to serve as the most commonly used criteria for ALS clinical trials. Methods A retrospective review of the Mayo Clinic Arizona EMG laboratory database was performed for patients with the diagnosis of motor neuron disease over a 2 year period. The clinical and EMG findings were reviewed in detail. Results The EMG database review revealed 125 patients with a diagnosis of motor neuron disease. Review of records revealed the final diagnosis was ALS in 112 of these and 13 were diagnosed with other forms of motor neuron disease. The clinical and EMG findings were reviewed in detail. In the ALS patients, a total of 1844 muscles were studied by EMG which represents an average of 16.5 muscles studied per patient. Of the 1,844 muscles studied, 649 were reported to show fasciculation potentials (34%) and 1067 showed fibrillation potentials (58%). None of the patients diagnosed with ALS had 0 muscles showing fibrillation potentials. However, 15 patients (12%) were reported to have 0 muscles showing fasciculation potentials. The number of ALS patients with 5 or fewer muscles showing fasciculation potentials was high at 54 (48%) compared to the number of ALS patients with 5 or fewer muscles showing fibrillation potentials, which was only 16 (14%). Conclusion This retrospective review of EMG findings in ALS patients suggests that fasciculation potentials are not identified as often as fibrillation potentials. All patients with a final diagnosis of ALS had fibrillation potentials on their EMG study whereas 12% of patients with a final diagnosis of ALS did not have fasciculation potentials identified on their EMG study. Thus, absence of fasciculation potentials should not be considered an unusual circumstance in ALS patients or an argument against the diagnosis of ALS. In contrast, fibrillation potentials are an expected finding in patients with ALS and the absence of fibrillation potentials does provide a strong argument against the diagnosis of ALS.

Introduction Carpal tunnel syndrome (CTS) is a common diagnosis that requires a thorough clinical history and examination. Electrodiagnostic (EDX) evaluation with nerve conduction studies (NCS) is frequently performed to assist the ordering physician when considering additional therapies or surgical intervention. It is a sensitive tool to examine median nerve dysfunction and aids in distinguishing CTS from cervical radiculopathy (CR) by identifying selective slowing of the conduction of median nerve fibers across the carpal tunnel. Some argue that if the NCS shows evidence of CTS, then needle EMG is not necessary. Current practice guidelines consider needle EMG to be an optional test better suited to exclude concurrent causes (cervical radiculopathy) of the patient’s symptoms for improving diagnostic sensitivity. We set out to determine the number of suspected CTS patients with evidence of CTS on NCS who also have concurrent needle EMG evidence of cervical radiculopathy. We aimed to further explore whether clinical examination performed by physicians ordering EDX could distinguish between the diagnoses of CTS and CR before testing is performed. Methods A retrospective chart review of 606 cases of CTS and CR in the Mayo Clinic Arizona EMG Laboratory from January 2015 to January 2016 was performed. Clinical notes of referring physicians for EMG/NCS and final EMG/NCS reports were reviewed for referring diagnoses, clinical history, physical exam and EMG diagnoses. Results Out of 472 patients diagnosed with CTS, 19.1% also had a concurrent diagnosis of CR confirmed by needle EMG ( n = 90). 17.2% of suspected CTS based on clinical assessment were not confirmed after electrodiagnostic testing ( n = 104). 29.0% of suspected CR patients were not confirmed after electrodiagnostic testing ( n = 176). 12 clinical assessment data points (clinical history and physical exam findings) felt to represent a common evaluation of diagnoses of CTS were compiled. These included cervicogenic pain, radicular pain, hand paresthesias, nocturnal pain, symptoms worse with activity, symptoms relieved by shaking out hands (“flick” sign), myotomal weakness, dermatomal sensory abnormalities, hyporeflexia, loss of sensation in the median nerve distribution, thenar atrophy, and hand weakness. The only clinical finding found to have a clinically significant association with both CTS and CR was hand paresthesias ( p = 0.001). Conclusion This series demonstrated that 19% of patients seen with CTS have an associated cervical radiculopathy. Without needle electromyography, these concurrent diagnoses would be missed, which can affect subsequent management and therapy. Clinical assessment alone may not be enough to distinguish between CTS and CR, as has been demonstrated in previous studies. Even though practice guidelines allude to optional needle EMG, this data provides a strong argument in favor of performing both NCS and needle EMG in patients with suspected CTS.