Horner syndrome may be present in Klumpke palsy. Horner syndrome occur in neonates with Klumpke palsy when the anterior root, spinal nerve, and proximal region of the ventral ramus are affected because these structures carry the sympathetic fibers that innervate the dilator muscle of the iris and the muscle of Müller. Horner syndrome does not occur with Kumpke palsy, which occurs as the result of an injury beyond the ventral ramus because the sympathetic fibers leave the brachial plexus at this level (Figure 221.1).

Figure 221.1.— Site of injury in Klumpke palsy. [A] Root of T1 and spinal nerve of C8. [B] Lower trunk. The green lines at T1 represent the most frequent origin of sympathetic fibers for the eyes. (PS): paraspinal muscles; (R): rhomboid muscle; DS: dorsoscapular nerve; LT: long thoracic nerve; (SA): serratus anterior muscle; (SS): supraspinal muscle; (IS): infraspinal muscle; SPS: suprascapular nerve; PL: pectoral lateralis nerve; (P): pectoralis muscle; PM: pectoralis medialis nerve; SF: sympathetic fibers to the eyes; (M of M): muscle of Müller; (DP): dilator pupillary muscle; (TM): teres major muscle; (SBS): subscapularis muscle; SBS: subscapularis nerves; TD: thoracodorsal nerve; (LD): latissimus dorsi muscle; MC: musculocutaneous nerve; (Bi): biceps muscle; (Br): brachialis muscle; M: median nerve; U: ulnar nerve; A: axillary nerve; (TMi): teres minor muscle; (D): deltoid muscle; R: radial nerve.

Horner syndrome manifests by ipsilateral ptosis and miosis. The eyelid asymmetry is not present when the patient cries or is asleep (Figure 221.2). The lack of pigmentation in the affected eye leads to a different color of the iris. This color difference is not noted in the immediate neonatal period nor is it noticeable in all patients. The color difference is noted if and when the iris of the eye not affected by the Horner syndrome becomes darker as the result of normal pigmentation. In the absence of Horner syndrome or the classical Klumpke posture of the arm, weakness restricted to the hand raises the possibility of a cortical lesion in the region of the hand. An MRI of the brain may be necessary to eliminate this possibility.

A	B

Figure 221.2.— Horner syndrome. [A] The right eye opening is smaller than the left when the patient is awake. [B] The asymmetric eye opening is not present when the neonate is crying.