Researchers at the Miami Children’s Hospital report 2 infants with obstetrical brachial plexus palsy, ipsilateral leg weakness, and contralateral motor cortical dysplasia. Case 1, an 18-month-old girl presented for evaluation of a left brachial plexus palsy that followed a delivery complicated by shoulder dystocia. At 3 months, the left leg moved less and was shorter than the right. At 6 months, following a febrile seizure, a head CT revealed a smaller right hemisphere, and an EEG showed vertex spikes. Right-sided motor cortex dysplasia was diagnosed by MRI at 11 months of age and confirmed at 24 months. MRI of the brachial plexus and spinal cord were normal. At age 18 months, neurologic examination showed restricted left arm abduction and elbow flexion, decreased left biceps and brachioradialis deep tendon reflexes, increased left patellar reflex, bilateral increase of Achilles tendon reflexes, left spontaneous Babinski, and shorter distance between the knee and ankle cutaneous creases on the left compared to the right leg.

Case 2, a 12-month-old boy with right brachial plexus palsy presented for evaluation of ipsilateral leg weakness, first noted by the mother when the infant attempted to walk. Neurological examination uncovered a tight right heel cord. Brain MRI revealed diffuse cortical dysplasia of the left hemisphere. [1]

COMMENT. The authors found no previous reports of an association of brachial plexus palsy and cortical dysplasia. They propose that this association helps explain the pathophysiology of brachial palsy in these patients by 2 mechanisms: prenatal shoulder girdle weakness and an abnormal arm position that increase the vulnerability of the plexus to stretch injury during delivery. Case 1 emphasizes the importance of attention to the length of the lower limbs and asymmetry in a neonatal neurological examination. MRI examination to exclude associated brain pathology should be considered in neonates with severe or complicated brachial plexus palsy.

Small Focal Cortical Dysplasia (FCD) lesions overlooked by routine MRI are visualized by high-resolution MRI, in a study at Montreal Neurological Institute, Canada [2]. Of 21 patients with small FCD, 17 (81%) were not identified initially, and 18 (86%) were located at the bottom of a sulcus. The knowledge that small FCD lesions are preferentially located at the bottom of an abnormally deep sulcus should aid the search for developmental cerebral lesions by routine MRI.

Outcome of Obstetric Brachial Plexus Injury correlates with force of downward traction of the fetal head in a study of 98 affected children at Goteborg University, Sweden [3]. At 18 months follow-up, 82% had recovered completely and 18% had persistent functional neurological deficits.