Differentials
Spinal muscular atrophy
SIGNS / SYMPTOMS
Several subtypes. Patient is floppy at birth and exhibits progressive weakness. There is no spasticity, but patients may develop contractures.
INVESTIGATIONS
DNA testing is available for most subtypes.
Muscle biopsy shows changes consistent with denervation, but no fibrosis.
Muscle enzymes are normal.
Electromyography reveals fascicular degeneration, fibrillation, repetitive discharge, and excessive polyphasic potentials, but is not necessary for diagnosis.
MRI reveals muscle loss in lower extremities.
Muscular dystrophy/myopathy
SIGNS / SYMPTOMS
No spasticity, but patients can develop contractures. There are various subtypes, including Duchenne's, Becker's, and limb girdle.
Child may be weak at birth or may have apparent normal development until approximate age 3 years, followed by a progressive loss of function and muscle weakness. There may be a positive family history.
Examination reveals a positive Gowers' sign with regression of walking ability.
Becker's type is less debilitating and manifests later in childhood. Limb girdle type may not present until late teens or 20s.
INVESTIGATIONS
Muscle biopsy reveals degeneration of cells, reductions in numbers of cells, and inflamed cells. Histochemical testing is possible for specific proteins.
Muscle enzymes are elevated.
Electromyogram identifies muscle as opposed to nerve disease and nerve conduction studies are normal.
DNA testing is available for many but not all subtypes.
Familial/primary dystonia
SIGNS / SYMPTOMS
Onset of muscular deformity occurs after several years of normal development.
Presents with sustained periods of muscle contraction and dystonia but without development of contractures. There may be abrupt and violent movements.
Positive family history.
INVESTIGATIONS
Molecular genetic testing is available.
Myelodysplasia
SIGNS / SYMPTOMS
Usually non-spastic. Associated spinal defect and a lack of sensation below a relatively specific spinal segment makes diagnosis obvious.
INVESTIGATIONS
Ultrasound and x-rays may be used to identify spine/spinal cord defects.
Familial (hereditary) spastic paraparesis
SIGNS / SYMPTOMS
Family history; progressive disease.
INVESTIGATIONS
Hereditary spastic paraparesis type 4 is the single most common dominantly inherited paraparesis, representing approximately 40% of cases. Genetic consultation may therefore be helpful.
Spinal stenosis/tethered cord
SIGNS / SYMPTOMS
Progressive neurological disease with worsening of the underlying neurology.
INVESTIGATIONS
MRI of spinal canal reveals the abnormality.
Brain tumour
SIGNS / SYMPTOMS
Initial development can be normal. Presents acutely with headache, raised intracranial pressure, seizures, and focal neurological deficits.
Occasionally coexists with CP.
INVESTIGATIONS
MRI reveals a space-occupying lesion.
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