What is the most likely diagnosis for a patient exhibiting scissoring of the legs when held upright with MRI findings of periventricular leukomalacia?

Cerebral Palsy with Spastic Diplegia

The diagnosis most strongly supported by scissoring gait and periventricular leukomalacia on MRI is bilateral lower limb spasticity (Option B), which is the hallmark clinical manifestation of spastic diplegia cerebral palsy. 1, 2

Clinical Presentation and Pathophysiology

Scissoring of the legs when held upright is a classic sign of bilateral lower extremity spasticity, specifically indicating spastic diplegia, the most common form of cerebral palsy associated with periventricular leukomalacia (PVL). 3, 2

• Periventricular leukomalacia is the pathological substrate found in 87% of preterm-born children with bilateral spastic cerebral palsy and 42% of term-born children with this condition. 2
• The white matter injury in PVL specifically affects the descending motor pathways that control the lower extremities more than the upper extremities, resulting in the characteristic diplegic pattern. 4, 5

Why Each Answer Choice Ranks as It Does

Option B (Bilateral Lower Limb Spasticity) - CORRECT

• This is the direct clinical manifestation of the underlying pathology shown on MRI. 2, 5
• Scissoring gait is pathognomonic for bilateral lower extremity spasticity, not merely a risk factor or associated finding. 3
• The spasticity is the functional outcome that defines the clinical syndrome, making it the most strongly supported diagnosis. 1

Option C (Prematurity) - Strong Association But Not "Diagnosis"

• While 87% of preterm infants with bilateral spastic CP have PVL, prematurity is a risk factor, not a diagnosis. 2
• The question asks what is "most strongly supported by the diagnosis" - prematurity is an etiological factor, not the clinical diagnosis itself. 1
• Importantly, PVL can occur in term infants (42% in one series), so prematurity is not universally present. 2

Option A (Static Motor Delay) - True But Non-Specific

• Cerebral palsy is by definition a static encephalopathy with motor dysfunction. 1
• However, "static motor delay" is too vague and non-specific - it doesn't capture the specific pattern of bilateral lower limb spasticity that scissoring represents. 1
• Many conditions cause static motor delay; this answer lacks the specificity that bilateral lower limb spasticity provides. 3

Option D (Periventricular White Matter Changes) - Already Given Information

• This is the MRI finding already stated in the question, not something "supported by the diagnosis." 4
• The question provides PVL as a given fact and asks what diagnosis this supports. 2

Correlation Between Imaging and Clinical Findings

MRI morphology correlates strikingly with clinical outcome in PVL: 2

• The characteristic MRI findings include reduction in periventricular white matter (particularly at the trigone), deep prominent sulci abutting ventricles, ventriculomegaly with irregular ventricular outline, and T2 hyperintensity in periventricular white matter. 4, 5
• The amount of white matter loss directly correlates with severity of motor disability, with greater reduction corresponding to more severe bilateral lower limb spasticity. 5
• Children with grade 2-3 PVL typically develop spastic diplegia (36%) or quadriplegia (48%), with 52% unable to walk independently. 6

Clinical Pitfalls to Avoid

• Do not confuse the imaging finding (PVL) with the clinical diagnosis - the imaging shows the anatomical substrate, but the clinical diagnosis is defined by the motor manifestation (bilateral lower limb spasticity). 1, 2
• Recognize that scissoring is specific for spasticity, not just general motor delay - this distinguishes spastic CP from athetoid or ataxic forms. 3
• Be aware that PVL in term-born children is associated with more severe disability than in preterm-born children with equivalent imaging findings. 2