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First described by Dubowitz in 1965,1 rigid spine syndrome represents an axial congenital merosin positive muscular dystrophy with early, predominant rigidity of the spine as its main characteristic trait. The illness begins at an early age with a delay in motor development, and affects more boys than girls; however, in some cases onset occurs slightly later when weakness of proximal limb muscles appears in a previously otherwise asymptomatic child. In all cases a limitation of neck and trunk flexion develops and scoliosis appears either simultaneously or in the ensuing years; later on the disease may progress slowly or tend to stabilise. Other features that accompany the musculoskeletal signs are respiratory disturbances and cardiac changes.2 Recently, a first locus for this syndrome has been identified on chromosome 1p.3 In laboratory studies serum creatine kinase concentrations can be raised. Electromyographic studies of paracervical musculature, trapezium, deltoid, biceps, and quadriceps show a myopathic pattern with normal nerve conduction velocities. Biopsy findings disclose non-specific myopathic changes with descriptions of type I fibre predominance, type II fibre predominance and fibre type disproportion; electron microscopic studies have detected the presence of Z band streaming.
It is important to distinguish rigid spine syndrome from other diseases in which rigidity of the spine can appear, such as Duchenne and Becker's muscular dystrophies, and principally from Emery-Dreifuss muscular dystrophy and from early onset ankylosing spondylitis, as prognoses are different. The rigid spine sign has also been reported in Bethlem myopathy and congenital myopathies such as nemaline myopathy. As in other muscular dystrophies, no more than supportive care can be offered to patients with rigid spine syndrome; surgical correction has been attempted on one occasion with success.4 Here we report a good response to botulinum toxin type A (BOTOX) treatment in a young man with rigid spine syndrome.
A 15 year old boy born at term, with congenital hypospadias surgically corrected and normal psychomotor development, was being studied by an endocrinologist because of short stature (mother's stature 145 cm, father's stature 169 cm) who noticed progressive neck flexion limitation and referred him to our institution. At admission on 8 July 1996, he complained of back pain since the previous year, which was more severe at rest; his mother had noticed a gait disturbance and that his back was progressively bending forward. General examination was normal; neurological examination showed no abnormal findings, and strength was completely preserved in all four limbs. He had marked postural kyphosis and contracture of neck extensors severely limiting movement in the anterior and lateral senses; hip flexion was severely affected (below 30º); no pain was produced by sacral manoeuvres. Radiological examination of the cervicothoracic spine showed scoliosis without vertebral malformations, 65º cervical lordosis involving C2 to C7, and a 55º thoracic kyphosis involving T3 to T12. Routine blood testing showed no abnormalities and creatine kinase concentrations were normal; autoantibodies routinely tested were negative. Complete spine MRI studies ruled out vertebral malformations. An ECG and radiography of the chest were normal. Radiological study of sacral joints was normal and the patient was not HLA-B27 positive. An EMG study showed a myopathic pattern (paraspinal musculature, periscapular musculature, and right quadriceps) with no abnormalities in nerve conduction. A biopsy of paraspinal musculature was performed and the neuropathological study of the muscle showed non-specific myopathic changes, including slight variability in muscle fibre size, occasional moth eaten fibres, and dilatations of the smooth endoplasmic reticulum, which were filled with fine granular material. The distribution and percentage of fibre types was preserved and no abnormalities in mitochondria and myofibres were seen. Immunohistochemistry to dystrophins, utrophin, and spectrin was normal. A diagnosis of rigid spine syndrome was made and botulinum toxin therapy was begun; with the aim of diminishing the imbalance between the neck flexor and extensor muscular groups to avoid fixed neck extension; for this reason we targeted muscles involved in head extension, principally the trapezium and secondly the esternocleiodomastoid and the paracervical musculature (table 1). During BOTOX therapy continuous improvement in neck flexion was seen, which was also perceived by the patient (fig 1). The radiological and functional measurements confirmed this assertion: in January 1996 the distance from chin to sternum was 10 cm in maximum neck flexion, in December 1997 this distance was 3 cm and in June 1999 the patient was able to touch his sternum with his chin. In march 1999 the patient developed myocarditis, with acute thoracic pain two weeks after a sore throat, increased creatine kinase concentrations, and electrocardiographic changes, with good recovery in 1 week. An echocardiogram performed 3 months later was normal and serology for Coxsackie virus was positive.
BOTOX is the trade mark of the commercialised typeA toxin of Clostridium botulinum; BOTOX causes muscle paralysis by acting at nerve endings and blocking presinaptically the release of quanta of acetylcholine5; this muscular paralysis is reversible and can ameliorate symptoms in patients with muscle spasms appearing as a manifestation of multiple neurological disturbances,6-8 including myopathies.9 10 In some situations this amelioration may become long lasting, and patients will not require further injections.11 The American Academy of Neurology recommends its therapeutic use in blepharospasm as a primary form of therapy; its use is accepted in cervical dystonia, adductor spasmodic dysphonia, jaw closing dystonia, and in hyperkinesis of hemifacial spasm; its use is considered promising in jaw opening and deviation dystonia, abductor spasmodic dysphonia, and in other focal dystonias.
The origin of spine stiffness in rigid spine syndrome is not well understood. Shortening of paraspinal ligaments or shortening of muscle fibres due to myofibrilar disorganisation have been invoked as possible origins of stiffness12; weakness of neck flexors can make this group of muscles incapable of counteracting extensor strength, finally causing spinal rigidity and cervical lordosis. Botulinum toxin may have an important part to play in preventing development of contractures and avoiding stiffness, not only in a symptomatic way, but also in a curative manner, as in our patient.
We thank Ms Julie Myers and Mr Josep Graells for linguistic assessment.
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