![]() See also sporadic stiff-man syndrome (184850) and the 'Jumping Frenchmen of Maine' (244100). Hyperekplexia can also occur in developmental and epileptic encephalopathy-8 (DEE8 300607), caused by mutation in the ARHGEF9 gene (300429). Genetic Heterogeneity of Hyperekplexia See also HKPX2 (614619), caused by mutation in the GLRB gene (138492) on chromosome 4q31 HKPX3 (614618), caused by mutation in the GLYT2 gene (SLC6A5 604159) on chromosome 11p15 and HKPX4 (618011), caused by mutation in the ATAD1 gene (614452) on chromosome 10q23. The symptoms tend to resolve after infancy, but adults may have increased startle-induced falls and/or experience nocturnal muscle jerks (summary by Ryan et al., 1992). Many affected infants have inguinal hernias. Neonates may have prolonged periods of rigidity and are at risk for sudden death from apnea or aspiration. ![]() Patients may also thrash around or act confused. ![]() Affected individuals have brief episodes of intense, generalized hypertonia in response to stimulation. Nocturnal seizures may range from awakening for no clear reason, sometimes multiple times a night, to shouting, screaming and violent movements of the arms and legs. Hyperekplexia is an early-onset neurologic disorder characterized by an exaggerated startle response to sudden, unexpected auditory or tactile stimuli. Some patients with DEPDC5 (614191) mutations may show features consistent with rolandic epilepsy (see FFEVF, 604364). Some patients with GRIN2A mutations show features consistent with a clinical diagnosis of BECTS. See also focal epilepsy and speech disorder (FESD 245570), which is caused by mutation in the GRIN2A gene (138253) on chromosome 16p13. Affected individuals may have learning disabilities or behavioral problems however, the seizures and accompanying problems usually remit during adolescence (summary by Strug et al., 2009). Rolandic epilepsy is considered a neurodevelopmental disorder, affecting 0.2% of the population. The disorder occurs more often in boys than in girls (3:2). Seizures most often occur in sleep shortly before awakening. Activity ranges from awakening from sleep for no clear reason, to violent arm and leg movement. This results in classic focal seizures that affect the vocal tract, beginning with guttural sounds at the larynx and sensorimotor symptoms that progress to the tongue, mouth, and face, resulting in hypersalivation and speech arrest. Nocturnal, or sleep-related seizures, cause abnormal movement or behavior while sleeping. It is termed 'rolandic' epilepsy because of the characteristic features of partial seizures involving the region around the lower portion of the central gyrus of Rolando. Benign epilepsy of childhood with centrotemporal spikes (BECTS) or sharp waves, also known as rolandic epilepsy, is the most common idiopathic childhood epilepsy syndrome (Neubauer et al., 1998).
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