Brain MR imaging findings in children with congenital muscular dystrophies

Congenital muscular dystrophies (CMDs) are a heterogeneous group of disorders presenting early in life during infancy or soon after birth with muscle weakness and hypotonia, sometime associated to severe brain involvement and histologically presenting with dystrophic lesions. They are classified on the basis of the clinical features, pathologic findings and pattern of inheritance. In fact most of these disorders are inherited and linked to specific genes. Several CDMs classifications have been proposed [1-3]. The main CMD subtypes, classified by pathogenic gene, are laminin alpha‐2 (merosin) deficiency (MDC1A), collagen VI-related CMD (COL6-RD), the dystroglycanopathies -such as Walker‐Warburg syndrome (WWS), Fukuyama CMD (FCMD), and muscle-eye-brain disease (MEB)-, SELENON (SEPN1)‐related CMD, and LMNA‐related CMD (L‐CMD) [4]. The incidence and prevalence of CMDs in various populations is not sufficiently known and may have been underestimated in early published CMD surveys owing to more limited diagnostic means available. Point prevalence in various studies ranges from 0.56 to 2.5 per 100,000 [5-10]. The relative frequency of CMD subtypes also varies in different populations. The most common CMD subtypes are laminin-α2 related CMD and dystroglycanopathies, followed by collagen VI-related CMD. The forms of congenital muscular dystrophy related to mutations in SEPN1 and LMNA are less frequent [9,11]. CMDs are often autosomal recessive, but some cases have been found to follow autosomal dominant patterns, by direct inheritance, spontaneous mutations, or mosaicism. Clinical genetic testing is available for virtually all genes known to be associated with CMDs. However, many affected individuals remain without a genetic diagnosis, an indicator that novel disease genes have yet to be identified [3]. Differential diagnosis of patients presenting with weakness in early infancy includes: Congenital myopathies like central core, nemaline road, and centronuclear myopathy and those secondary to metabolic disorders; Disorders of the myoneural junction including congenital myasthenia gravis and infant botulism and Neuropathies like spinal muscular atrophy (SMA) and hereditary motor sensory neuropathy (HMSN) [12]. Nowadays the diagnosis is based on clinical presentation, laboratory tests and genetic investigations. Muscular biopsy can be an important diagnostic tool if genetic tests are not available. Brain MRI and muscular MRI are performed if available. We discuss brain MR imaging findings in our patients with CMDs trying to outline common features and differences in order to aid in the diagnosis of these rare disorders before performing genetic tests.