Werdnig-Hoffmann Disease
Werdnig-Hoffmann disease or spinal muscular atrophy type I is an autosomal recessive disorder caused by premature death of the alpha motor neurons. A history of decreased and weak fetal movements in the last trimester is often present. Neonates with Werdnig-Hoffmann disease may have different presentations: (1) hypotonia from birth, (2) an acute onset of hypotonia and weakness after an apparently normal period, or (3) acute onset of respiratory failure. Hypotonia from birth is the most common presentation.
Werdnig-Hoffmann disease usually presents with hypotonia and decreased dynamic tone. Hypotonia and decreased dynamic tone affects the axial musculature more than the appendicular musculature, the proximal muscles more than the distal muscles, the lower extremities more than the upper extremities, the lower cranial nerve muscles more than the upper cranial nerve muscles, and, in most cases, the intercostal muscles more than the diaphragm.
The tongue of a neonate with Werdnig-Hoffmann disease may be weak, thin, and have clinical fasciculations. Fine rhythmic tremor of the finger may be present (polyminimyoclonus). Neonates with Werdnig-Hoffmann disease look alert. They do not have ptosis, ophthalmoplegia, or sphincter or sensory disturbances. Serum creatine phosphokinase, sensory nerve conduction, and motor nerve conduction in the neonatal period are normal.