Entrapment Mononeuropathies in Children
Carpal Tunnel Syndrome in Children
Carpal tunnel syndrome (CTS) is a relatively rare complication in children, with mucopolysaccharidosis types I, II, and III (eg Hunter's and Hurler's syndromes) and mucolipidosis being the most common populations to manifest CTS during childhood (94).
Treatment of the metabolic disorder does not necessarily reverse the symptoms, and prompt surgical release is necessary. Other uncommon etiologies include hereditary neuropathies such as CMT 1 and hereditary neuropathy with liability to pressure palsies (HNPP), CIDP, treatment with growth hormone, hemophilia with localized bleeding in the region of the carpal tunnel, Schwartz- Jampel syndrome, multiple xanthomas associated with familial hypercholesterolemia, congenital macrodactily in a median nerve territory, fibrolipomas of the median nerve, and Klippel-Trenauny syndrome (95).Ulnar Mononeuropathies in Children
Ulnar mononeuropathies are the most common upper extremity mononeuropathies seen in children (96). The most common etiology is acute trauma (eg, midshaft or proximal forearm fractures, elbow dislocation, etc.), compression from compartment syndrome, or entrapments in association with HNPP or other anomalous anatomy producing entrapment. Other etiologies include baseball throwing injuries in adolescents, Larsen's syndrome with dislocations, congenital constriction band syndrome, insulin-dependent diabetes mellitus, leprosy, and so on. The location of the neuropathy is most commonly the cubital tunnel, but it may also localize to the forearm, wrist, or hand.
Radial Mononeuropathies in Children
Radial mononeuropathies are rare but do occur in children. In one series, 50% of radial neuropathies, including two in newborns with apparent prenatal onset, were atraumatic, primarily related to compression in six and entrapment in two.
The other 50% were traumatic mononeuropathies related to fractures or lacerations (97). Electromyography documented the radial neuropathy to be localized to the proximal main radial nerve trunk in 13%, distal main radial nerve trunk in 56%, and posterior interosseous nerve in 31% of children.Peroneal Mononeuropathies in Children
The most common entrapment in the lower extremity is peroneal mononeuropathy at the fibular head. Children with peroneal mononeuropathy typically present with unilateral foot drop. Both distal branches are involved in the majority of cases; hence, the level of the lesion is most often the common peroneal nerve at or above the fibular head, followed by the deep peroneal nerve and superficial peroneal nerve (98). Common etiologies include compression from a short leg cast, compression from prolonged surgical positioning, and trauma (eg, distal femoral physeal fractures, proximal tibial fractures, etc.). Contributing factors include hereditary neuropathies (CMT or HNPP) and significant rapid weight loss in an adolescent. Other etiologies may include compression from osteochondromas, neurofibromas, and intraneural ganglions; arthrogenic cyst of the fibula; and stretch during tibial limb lengthening.
Sciatic Mononeuropathies in Children
Sciatic mononeuropathies are uncommon in children. Etiologies in one series included compression, stretch injuries (eg, during closed reduction of a hip dislocation), lymphoma, vasculitis associated with hypereosinophilia, and penetrating trauma (99). The peroneal division is more commonly affected than the tibial division in the absence of penetrating trauma. The vascular supply to the peroneal division may be more susceptible to compromise from stretch or compression. Axonal sciatic lesions are more common than demyelinating lesions.
Neuropathies With Limb-Lengthening Procedures
Mononeuropathies in the setting of limb lengthening are not uncommon, but are frequently subclinical. Patients undergoing tibial limb lengthening procedures are at risk for peroneal neuropathies in particular and rarely tibial mononeuropathies. Femoral lengthening can place a patient at risk for neuropathies affecting the sciatic nerve (particularly the peroneal division). Humeral lengthening can place upper extremity nerves at risk. Some have monitored for subclinical neuropathy of the upper and lower extremities using mixed- nerve somatosensory-evoked potentials during pin placement and serially during distraction (100,101).