Craneosinostosis

Overview of disorders of peripheral nerves and muscle causing hypotonia in the newborn
Last literature review version 18.2: mayo 2010 | This topic last updated: enero 15, 2010 (More) INTRODUCTION — Newborns with neuromuscular disorders often present with hypotonia and weakness. (See "Approach to the infant with hypotonia and weakness".) These disorders are caused by a variety of conditions thataffect the central nervous system (brain or spinal cord), peripheral nervous system, or skeletal muscle. Conditions that affect the last two sites are reviewed briefly here (table 1). More complete discussions of these conditions and of disorders caused by upper motor neuron lesions that involve the descending motor tracts within the brain and spinal cord and of other systemic conditions (eg,Prader-Willi syndrome, Angelman syndrome, multiple minor congenital anomaly syndromes, or inborn errors of metabolism) are presented elsewhere. (See "Clinical features, diagnosis, and treatment of Prader-Willi syndrome" and "Overview of the classification of inborn errors of metabolism" and "Overview of the evaluation of inborn errors of metabolism in children" and "Presenting features of inborn errorsof metabolism".) ANTERIOR HORN CELL DISORDERS — Many conditions are caused by degeneration of the anterior horn cells of the spinal cord. They include spinal muscular atrophy, traumatic myelopathy, hypoxic-ischemic myelopathy, and neurogenic arthrogryposis. (See "Spinal muscular atrophy".) Spinal muscular atrophy — The most common and severe type that presents in newborns is spinal muscularatrophy (SMA) type 1, also known as Werdnig-Hoffmann disease. This condition should be suspected in infants with diffuse symmetric proximal muscle weakness that is greater in the lower than upper limbs and absent or markedly decreased deep tendon reflexes. SMA types 2 and 3 have later onset and are less severe. Traumatic myelopathy — Myelopathy caused by trauma to the high cervical spinal cord is arare cause of hypotonia in infants. This condition results in a flaccid paralysis, which may be asymmetric, and absent reflexes. Hypoxic-ischemic myelopathy — Severe hypoxic-ischemic injury occasionally can result in hypotonia or flaccid paralysis with diminished or absent reflexes. Affected infants typically have encephalopathy and may have seizures or other signs of end-organ damage. Arthrogryposismultiplex congenita — Arthrogryposis (joint contractures) multiplex congenita is a heterogeneous group of disorders characterized by contractures of multiple joints and degeneration of motor neurons. Most cases are neurogenic; the remainder result from primary muscle disease. CONGENITAL MOTOR OR SENSORY NEUROPATHIES — Congenital motor or sensory neuropathies can cause hypotonia and weakness thatpresent during the neonatal period or early infancy. The most important of these conditions are the congenital motor sensory neuropathies and the hereditary sensory and autonomic neuropathies. Congenital motor sensory neuropathies — Congenital motor sensory neuropathies (HMSNs) comprise a heterogeneous group of disorders that affect the peripheral nervous system. HMSNs represent a spectrum ofdiseases caused by mutations in one of several myelin genes that result in defects in myelin structure, maintenance, or formation. Charcot-Marie-Tooth disease is the most common of these conditions. (See "Hereditary primary motor sensory neuropathies, including Charcot-Marie-Tooth disease".) Hereditary sensory and autonomic neuropathies — Hereditary sensory and autonomic neuropathies (HSANs) are agroup of rare disorders that selectively affect peripheral sensory and autonomic neurons (table 2). They present in infancy and result in a variable extent of autonomic dysfunction or insensitivity to pain and

temperature. The most common HSAN is familial dysautonomia (Riley-Day syndrome). (See "Hereditary sensory autonomic neuropathies".) NEUROMUSCULAR JUNCTION DISORDERS — Disorders of the...