Other neurological findings
that may help to localize the lesion in a patient with spastic arm weakness
are the presence of seizures and gaze preference. Seizures are more common
with cortical or subcortical lesions than with lesions below these areas.
Convulsions usually involve the weak arm and may become generalized. Gaze
preference may occur with spastic arm weakness.
arm weakness is due to a focal central nervous system lesion. The evaluation
of a neonate with spastic arm weakness should include MRI and MRA of the
brain. Magnetic resonance imaging and angiography of the brain usually
localize the lesion. If the MRI and the MRA are normal, an MRI of the
upper cervical spine should be done.
flaccid arm monoplegia have decreased frequency and strength of movement
of the affected limb (Figure 211.1 [A]). They also show absence or decreased
movement during the Moro reflex (Figure 211.1 [B]) and decreased biceps,
brachioradialis, and triceps muscle stretch reflexes. The location of
the lesion in a neonate with flaccid weakness may be in the upper motor
neuron or in the lower motor neuron.
Figure 211.1.— Flaccid arm monoparesis. [A] The left arm rests
motionless. [B] The Moro reflex does not elicit movement of the weak arm.