Differential Diagnosis of Lower Extremity Neurological Lesions

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Differential Diagnosis of Lower Extremity Neurological Lesions

Important step in diagnosis of neurological problems is “Where is the lesion?”

Upper motor neuron pathway and corticospinal tract lesions:
Negative features – muscle weakness, fatigue, decreased dexterity
Positive features – increased tendon reflexes (hyperreflexia); clonus; positive Babinski’s sign; spasticity; dyssynergic patterns of co-ordination during movement; extensor and flexor spasms (most commonly hip, knee and ankle)
eg primary lateral sclerosis, spastic paraparesis

Cerebellum lesions:
Ataxia – clumsiness in the legs; balance problems; intention tremor; hypotonia; difficulty with complex movements

Basal ganglia lesions:
Chorea, athetosis, myoclonus, involuntary movements, dystonia

Lower motor neuron pathway lesions:
Atrophy, weakness, fasciculations, decreased tone, reduced reflexes (hyporeflexia)
eg poliomyelitis

Difference Between Upper (UMNL) and Lower Motor Neurone (LMNL) Lesions:
Sensory Loss Diffuse Dermatome
Weakness Diffuse Individual muscles
Muscle bulk Normal (some from disuse) Atrophy
Lower extremity tone Usually spastic Flaccid
Paresis Contralateral to lesion Limited to specific group
Deep tendon reflexes Increased (hyperreflexia) Decreased (hyporeflexia)
Babinski’s sign Present Absent
Tremor Present Absent

Nerve root lesions (radiculopathy):
In dermotomal the distribution of nerve root involved  pain, motor and sensory deficits. Pain in region of origin of nerve root may be present on palpation. Muscle weakness in dermatomal distribution.

Neurological features of lumbar and sacral spinal nerve root lesions
Nerve Root Symptoms (excluding pain) Pain Signs
L-1 Paraesthesia in region of trochanter and upper groin No motor or reflex changes
L-2 Paraesthesia in anterior thigh Diagonally across thigh Weakness of psoas – weakness of hip flexion
L-3 Paraesthesia in anterior and medial knee and anterior lower leg – may also get quadriceps weakness ad atrophy Diagonally across thigh Weakness of psoas and quadriceps. Knee reflex depressed or normal
L-4 Paraesthesia in medial lower leg and ankle – may get quadriceps weakness, atrophy and footdrop Down to medial malleolus – may be severe around knee Weakness of quadriceps, tibialis anterior and posterior, knee jerk depressed
L-5 Paraesthesia in anterolateral lower leg and dorsum of foot – may get footdrop
Positive straight leg raise Back of thigh, lateral calf and lateral ankle, dorsum of foot, dorsal hallux Weakness of tibialis anterior, toe extensors peroneal and gluteal muscles. Ankle jerk may be decreased
S-1 Paraesthesia in sole and lateral border of foot and ankle. Sometimes 3rd and 4th toes numb. May get weakness of foot plantarflexion
Posterior thigh, posterior calf, lateral foot, heel Weakness of gastrocnemius, toe flexors, peroneal and gluteal muscles. Ankle reflex depressed
S-2 Parathesia in posterior leg – may get weakness of plantarflexion of foot Weakness of gastrocnemius and toe flexors. Ankle reflex depressed
S-3 Parathesia in upper medial thigh and medial buttock No muscle weakness or reflex change

Lumbosacral plexus lesions:
Sensory and motor deficits along distribution of nerve(s) affected.

Femoral nerve lesions:
Atrophy of anterior thigh; hip flexion weakness; reduced patellar reflex; sensory loss or pain anteromedial thigh and medial lower leg; pain anterior thigh, medial leg and ankle.

Sciatic nerve lesions:
Atrophy of weakness of lower limb muscles; may have foot drop; sensory deficits on lateral leg, plantar and dorsal foot; achilles reflex may be diminished

Common peroneal nerve lesions:
Weakness of dorsiflexion and eversion of foot; weakness of toe dorsiflexion and foot inversion; sensory deficits over dorsum of foot; dull ache over anterolateral leg and foot

Tibial nerve lesions:
Sensory changes on plantar surface and lateral foot. Weakness of plantarflexion and inversion.

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