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Muscle Cramps Associated with Localized Scleroderma Skin Lesions: Focal Dystonia, Neuromyotonia, or Nerve Entrapment? To the Editor: Localized scleroderma is a relatively benign and self-limited condition, with manifestations mostly restricted to the skin and subdermal tissue without vascular or visceral involvement1. The pathogenesis and etiology of this disease remain controversial. It has been speculated that localized scleroderma may develop as a response to neurologic injury2. We describe the occurrence of muscle cramps in the distribution of skin lesions in 3 patients with localized scleroderma and review the literature. Case 1. A 36-year-old woman with established linear scleroderma developed a new hypo- and hyperpigmented skin lesion extending linearly from the dorsum of the right hand, over the forearm, and continuing in a band-like distribution to the biceps and deltoid areas. As the skin lesion enlarged over several months, she complained of muscle cramping involving the right triceps, biceps, and forearm muscles. Forearm cramps were elicited with chopping motions, and writing precipitated wrist and finger flexor muscle cramping. She was treated with hydroxychloroquine 200 mg bid. D-penicillamine and prednisone were previously discontinued. Cranial nerves, muscle strength, coordination, sensory examination, and deep tendon reflexes were normal. Cervical spine magnetic resonance imaging (MRI) revealed mild C5–C6 central disc herniation. Electromyography documented co-contraction of the right biceps and triceps muscles. Laboratory testing showed normal creatine kinase (CK) and a positive antinuclear antibody in a titer of 1:160 (normal < 40) with speckled staining, positive single-strand DNA antibody test, and hypergammaglobulinemia. Case 2. A 40-year-old woman with morphea complained of episodic right arm pain and cramping of the right third and fourth fingers, sometimes accompanied by sustained ulnar deviation of the wrist. These symptoms were elicited by writing. On examination she had hyperpigmentation and atrophy extending from just beneath the axilla down the inner aspect of the arm to the distal forearm. There was a pale, slightly indurated and thickened area over the right buttock. Cranial nerves, muscle strength, coordination, sensory examination, and deep tendon reflexes were normal. There were no spontaneous or inducible involuntary movements. Electromyography was normal. Cervical spine MRI was normal. Laboratory testing included normal CK and negative anti-single-strand DNA antibody test. Case 3. A 19-year-old woman with linear scleroderma developed dysesthesias and muscle cramping of the right fourth and fifth fingers. Muscle cramping was not task-induced. She also complained of dysesthesias and "a pulling sensation" in the left upper quadrant of the abdomen. She was previously treated with hydroxychloroquine. Mental status, muscle strength, coordination, and deep tendon reflexes were normal. Hyperpigmented skin with atrophic subcutaneous tissue extended from the medial aspect of the right forearm to the right hypothenar area. Similar hyperpigmented skin lesions with atrophy were present in the left upper abdomen. There was also atrophy of the left side of the tongue. Sensation to light touch was decreased with hypersensitivity to pinprick in the right C8, T1 and T2, and left T8 and T9 dermatomes. There were no spontaneous or inducible involuntary movements. Three years earlier, at the onset of symptoms, nerve conduction studies showed mild distal right ulnar mononeuropathy. MRI of the cervical spine showed mild hypertrophy of the right C3-C4 and C5-C6 facets with mild foraminal narrowing at C6-C7. Laboratory testing showed normal CK and an elevated anti-single-strand DNA antibody (219 units/ml; normal < 60). Muscle cramp is a sudden involuntary shortening of the muscle occurring at rest or with muscle activation (contraction). Shortened muscle is more susceptible to muscle cramps3, as seen in atrophic regions affected by localized scleroderma. The presence of agonist-antagonist co-contraction in one of our patients is suggestive of focal dystonia. The peripheral origin of dystonia remains controversial, and proposed mechanisms include altered sensory input or increased spinal cord excitability after peripheral nerve injury (entrapment)4,5. Muscle cramps caused by continuous muscle fiber activity6 and neuromyotonia7,8 have been reported in 3 other patients with contiguous scleroderma skin lesions (Table 1).
Localized scleroderma may affect subcutaneous and deeper tissues, including muscles, ligaments, and bone, leading to stretching, angulation, or compression of nerves, followed by focal demyelination of motor nerve fibers. Dermatomal distributions of localized scleroderma skin lesions have been observed by some authors, and the skin lesions may follow a nerve injury2. The occurrence of muscle cramps in the distribution of skin lesions may be attributable to nerve hyperexcitability (leading to neuromyotonia or dystonia) or ephaptic transmission, similar to hemimasticatory spasm9. In systemic sclerosis, distal axonopathy and focal nerve entrapment usually do not correspond to the distribution of skin lesions and are not associated with prominent muscle cramps10. Based on the temporal and spatial correlation of skin lesions and muscle cramps in our patients, we propose that localized scleroderma may precipitate muscle cramps, possibly caused by local nerve injury. Additional studies are needed to define the pathophysiology of such muscle cramps and to establish the spectrum of neurologic complications of localized scleroderma. SASA A. ZIVKOVIC, MD, VA Pittsburgh Healthcare System and Department of Neurology, University of Pittsburgh School of Medicine; DAVID LACOMIS, MD, Department of Neurology and Department of Pathology (Neuropathology), University of Pittsburgh School of Medicine; THOMAS A. MEDSGER Jr, Department of Medicine, Division of Rheumatology and Clinical Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA. Address reprint requests to Dr. S.A. Zivkovic, Department of Neurology, University of Pittsburgh Medical Center, PUH F875, 200 Lothrop St., Pittsburgh, PA 15213. E-mail: zivkovics@upmc.edu REFERENCES 1. Falanga V, Medsger TA Jr, Reichlin M, Rodnan GP. Linear scleroderma. Clinical spectrum, prognosis, and laboratory abnormalities. Ann Intern Med 1986;104:849-57. [MEDLINE] 2. Littman BH. Linear scleroderma: a response to neurologic injury? Report and literature review. J Rheumatol 1989;16:1135-40. [MEDLINE] 3. Layzer RB. The origin of muscle fasciculations and cramps. Muscle Nerve 1994;17:1243-9. [MEDLINE] 4. Ross MH, Charness ME, Lee D, Logigian EL. Does ulnar neuropathy predispose to focal dystonia? Muscle Nerve 1995;18:606-11. [MEDLINE] 5. Sankhla C, Lai EC, Jankovic J. Peripherally induced oromandibular dystonia. J Neurol Neurosurg Psychiatry 1998;65:722-8. [MEDLINE] 6. Papadimitriou A, Chroni E, Anastasopoulos I, Avramidis T, Hadjigeorgiou G, Koutroumanidis M. Continuous muscle fiber activity associated with morphea (localized scleroderma). Neurology 1998;51:1763-4. [MEDLINE] 7. Benito-Leon J, Miguelez R, Vincent A, Masjuan J, de Blas G. Neuromyotonia in association with systemic sclerosis. J Neurol 1999;246:976-7. [MEDLINE] 8. Kumar A, Jain R, Daga J. Simultaneous occurrence of neuromyotonia and morphoea: a cause-effect relationship? J Neurol Neurosurg Psychiatry 2006;77:802. [MEDLINE] 9. Cruccu G, Inghilleri M, Berardelli A, et al. Pathophysiology of hemimasticatory spasm. J Neurol Neurosurg Psychiatry 1994;57:43-50. [MEDLINE] 10. Poncelet AN, Connolly MK. Peripheral neuropathy in scleroderma. Muscle Nerve 2003;28:330-5. [MEDLINE]
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