Extensive somatosensory innervation in infants with obstetric brachial palsy

Abstract

In the pre-operative screening of infants with obstetric brachial palsy (OBP), the results of routine electromyography are often overly optimistic when compared to the peri-operative findings. This prompted us to include investigation of the sensory innervation of these infants using the N20 (the first cortical response to a peripheral stimulation) of the somatosensory evoked potentials (SSEP). Three to seven months after birth, SSEP were recorded at the skull after stimulation of the thumb and middle finger in infants with obstetric rupture of the upper trunk or avulsion of roots C5, C6, or C7, and in whom no clinical improvement of motor function was observed in the biceps brachii and deltoid muscles. In most infants, a normal N20 could be evoked, indicating the existence of peripheral sensory pathways. From the thumb, these sensory pathways would necessarily bypass the upper trunk and dorsal roots of spinal nerves C5 and C6, and from the middle finger bypass the middle trunk and dorsal root C7, before extending into the dorsal column and projecting toward the thalamus and cerebral cortex. These data suggest that in infancy the segmental sensory innervation of the hand is more diverse than is described in most textbooks.

A cross‐sectional study of hand sensation in adults with conservatively treated obstetric brachial plexus lesion

“…Our findings agree with Colon et al. : 25 there is reasonably good sensation in skin areas in which profound deficits might be expected. The absence of such major ‘gaps’ in sensation in OBPL may be explained partly by the fact that in most infants with OBPL there is no anatomical gap between two torn nerve stumps.…”

Prognostic value of thumb pain sensation in birth brachial plexopathy

“…One possible explanation is that the dermatomes overlap extensively; so, many adjacent spinal levels should be compromised in order to generate a sensory deficit 19 . Collon et al also suggested the possibility of alternative paths for peripheral sensory information in young infants with brachial plexus lesions 20 . One very tempting explanation is related to the physiopathology of neurapraxia 21 .…”

Early electrodiagnosis in the management of neonatal brachial plexus palsy: A systematic review

“…Comparatively, imaging had a specificity of 29.4% at C8 and 57.1% at T1. Finally, the use of preoperative SEP showed no value in determining severity of the plexus lesion as it may be confounded by the persistence of the fetal polyneuronal innervation of the somatosensory system in children with NBPP …”