Differential Diagnosis and Cerebral Palsy
Motor skills that decline over time may indicate genetic disease, muscle or metabolic disorder, or tumor in the nervous system, either coexistent with or instead of CP. The physician must rule out other disorders that cause movement problems, identify any coexisting disorder, and determine if the condition is changing.
An electroencephalogram (EEG) traces electrical activity in the brain and can reveal patterns that suggest a seizure disorder.
Electromyography (EMG) and nerve conduction velocity (NCV) studies may be performed when a nerve or muscle disorder is suspected. These tests, which can be used in combination, are often referred to as EMG/NCV studies. NCV is administered before EMG and measures the speed at which nerves transmit electrical signals.
During NCV, electrodes are placed on the skin over a nerve that supplies a specific muscle or muscle group. A mild, brief electrical stimulus is delivered through the electrode and the response of the muscle is detected, amplified, and displayed. The strength of the signal is also measured. Neurological conditions can cause the NCV to slow down or to be slower on one side of the body.
EMG measures nerve impulses within the muscles. Tiny electrodes are placed in the muscles in the arms and legs and the electronic responses are observed using an instrument that displays movement of an electric current (oscilloscope). As muscles contract, they emit a weak electrical signal that can be detected, amplified, and tracked, providing information about how well the muscles are working.
Laboratory Tests and Cerebral Palsy Diagnosis
Chromosome analysis may be performed to identify a genetic anomaly (e.g., Down syndrome) when abnormalities in features or organ systems are present.
Thyroid function tests may reveal low levels of thyroid hormone, which can produce several congenital defects and severe mental retardation.
A high level of ammonia in the blood (hyperammonemia) is toxic to the central nervous system (i.e., brain and spinal cord). A deficiency in any of the enzymes involved in breaking down amino acids can cause hyperammonemia. This may be due to a liver disorder or a defect in metabolism.
Imaging Tests and Cerebral Palsy Diagnosis
Imaging tests are helpful in diagnosing hydrocephalus, structural abnormalities, and tumors. This information can help the physician assess the child's long-term prognosis.
Magnetic resonance imaging (MRI scan) uses a magnetic field and radio waves to create pictures of the internal structures of the brain. This study is performed on older children. It defines abnormalities of white matter and motor cortex more clearly than other methods.
Computed tomography (CT scan) can show congenital malformations, hemorrhage, and periventricular leukomalacia in infants.
Ultrasound uses the echoes of sound waves projected into the body to form a picture called a sonogram. It is often used in infants before the bones of the skull harden and close to detect cysts and abnormal structures in the brain.