Investigators from Armand-Trousseau hospital and University of Paris studied 90 infants aged birth to 6 months with multiple cranial nerve involvement. Neurophysiologic studies using blink responses (BR’s) and electromyography (EMG) of the muscles of the face, tongue and soft palate were performed to investigate for orofacial function.
Neurogenic pattern was noted with involvement of facial nerve in 82/90 patients, abnormal BR’s in 40/63, pharyngeal plexus in 56/89 and hypoglossal nerve in 25/90. Poor outcome (presence or absence of neurological disabilities, need for respiratory assistance, gastrostomy and prolonged enteral feeding) and death was higher (P=0.02) where EMG identified >= 4 affected cranial nerves. There was however no significance associated with involvement of lower cranial nerves and poor outcome. 
COMMENTARY. Studies of cranial nerves in children using EMG is a time intense process involving a trained electromyographer and equally trained supportive staff. The investigators previously published studies where orofacial EMG’s were performed in children  for assessing brainstem involvement  and dysphagia in infants with facial malformations . They combined the techniques to study all children referred to their center for orofacial dysfunction and observed outcome related to the number of cranial nerves involved.
Orofacial dysfunction is assumed to be of suprabulbar origin and although the cerebral cortex is more vulnerable to ischemia, neuropathological studies have shown brainstem involvement in birth asphyxia  and prenatal ischemia  . There are reports of hypoglossal involvement in children where periventricular leukomalacia or hemorrhagic infarction was thought to be the cause of dysphagia . In fact, 14 patients of this study were thought to have a cortical vascular insult at birth with orofacial dysfunction but EMG studies showed face, tongue and soft palate neurogenic changes.
The study highlights that EMG’s are not only useful for peripheral nerves and the muscles they innervate, but can be employed for cranial nerve assessment. Localizations with respect to brainstem pathology can be inferred by testing multiple cranial nerve innervations in the facial and bulbar muscles. Neurophysiology is also helpful as clinical exam alone detected 3 times less facial nerve involvement compared to EMG, especially when the involvement was bilateral. EMG aided in diagnosis of lingual and pharyngeal abnormalities that were difficult to pick up clinically.
This study also underscores a poor outcome based on the number of cranial nerve involvement and not the cranial nerve type based on location in the brainstem. It is surprising that lower cranial nerves thought to induce a higher risk of airway compromise and aspiration, were not associated with poor outcome.
The author(s) have declared that no competing interests exist.
Renault, F, Flores-Guevara, R, Baudon, JJ and Vazquez, MP (2015). Congenital multiple cranial neuropathies: relevance of orofacial electromyography in infants. Muscle Nerve Nov 201552(5): 754–758, DOI: https://doi.org/10.1002/mus.24636 [PubMed]
Renault, F Baudon, JJ Galliani, E Flores-Guevara, R Marlin, S Garabedian, EN et al. (2011). Facial, lingual, and pharyngeal electromyography in infants with Pierre Robin sequence. Muscle Nerve Jun 201143(6): 866–871, DOI: https://doi.org/10.1002/mus.21991 [PubMed]
Renault, F, Flores-Guevara, R, Soupre, V, Vazquez, MP and Baudon, JJ (2000). Neurophysiological brainstem investigations in isolated Pierre Robin sequence. Early Hum Dev May 200058(2): 141–152, DOI: https://doi.org/10.1016/S0378-3782(00)00073-6 [PubMed]
Baudon, JJ Renault, F Goutet, JM Biran-Mucignat, V Morgant, G Garabedian, EN et al. (2009). Assessment of dysphagia in infants with facial malformations. Eur J Pediatr Feb 2009168(2): 187–193, DOI: https://doi.org/10.1007/s00431-008-0729-7 [PubMed]
Leech, RW and Alvord, EC Jr (1977). Anoxic-ischemic encephalopathy in the human neonatal period. The significance of brain stem involvement. Arch Neurol Feb 197734(2): 109–113, DOI: https://doi.org/10.1001/archneur.1977.00500140063013 [PubMed]
Alvord, EC Jr and Shaw, CM (1989). Congenital difficulties with swallowing and breathing associated with maternal polyhydramnios: neurocristopathy or medullary infarction?. J Child Neurol Oct 19894(4): 299–306, DOI: https://doi.org/10.1177/088307388900400410 [PubMed]
Vijayakumar, K, Rockett, J, Ryan, M, Harris, R, Pitt, M and Devile, C (2012). Experience of using electromyography of the genioglossus in the investigation of paediatric dysphagia. Dev Med Child Neurol Dec 201254(12): 1127–1132, DOI: https://doi.org/10.1111/j.1469-8749.2012.04431.x [PubMed]