EMQs in Clinical Medicine.pdf - Peshawar Medical College

Weakness in the legs – answers 93
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A 55-year-old man presents with bilateral progressive worsening
muscle weakness. There is marked wasting of lower limb muscles and
very brisk lower limb reflexes. Sensation is normal.
Motor neuron disease (MND) is a progressive degenerative disease that
affects the upper and lower motor neurons (LMNs). There is characteristically
NO sensory involvement.
It is useful to be familiar with the following three common patterns of
involvement:
(i) Progressive muscular atrophy: anterior horn wasting lesion with
wasting often beginning in the distal muscles of the hand and then
spreading. Fasciculation is a common finding.
(ii) Amyotrophic lateral sclerosis: involvement of the lateral corticospinal
tract gives a progressive spastic teraparesis/paraparesis.
The presence of LMN signs, e.g. wasting, fasciculation, differentiates
this diagnosis from other causes of spastic weakness.
(iii) Progressive bulbar palsy: the lower cranial nerve nuclei and their
connections are primarily affected. Dysarthria and dysphagia are
common symptoms. This pattern of disease is more common in
women than in men.
A 13-year-old boy presents with bilateral pes cavus with clawing of
the toes. There is atrophy of peroneal muscles and reduced reflexes
and sensation distally.
Charcot–Marie–Tooth disease is a progressive peroneal muscle atrophy.
There are both autosomal dominant and recessive inheritances observed
in different families. Charcot–Marie–Tooth disease is now described as a
hereditary sensorimotor neuropathy (HSMN) because several clinical
variants have been identified associated with different gene defects.
HSMN types I and II are the most common types.
HSMN type I is a demyelinating neuropathy of insidious onset presenting
typically in the first decade of life with foot deformities (e.g. pes cavus),
muscle weakness (distal weakness that affects legs earlier and more
severely than arms) and loss of balance. The presence of foot drop results
in frequent trips and falls.
HSMN type II usually presents later in the second decade of life. The
weakness in distal lower limb muscles is often accompanied by distal
sensory loss. Foot deformities are less marked than in type I disease and
patients may even be completely asymptomatic.
A 30-year-old secretary presents with bilateral leg weakness
and blurred vision. Fundoscopy reveals pale optic discs
bilaterally.
In this case the pale bilateral optic discs indicate previous subclinical
episodes of optic neuritis. Multiple sclerosis (MS) is an inflammatory