4th article Flashcards
A 61-year-old woman presented to her primary care physician with
- a 4-week history of progressive bilateral leg weakness, 2. bilateral leg pain, and
- difficulty walking.
The weakness was
symmetric, without exacerbating or ameliorating factors, and did not fluctuate during the course of the day.
The patient also reported
- depression,
- anxiety,
- memory problems, and
- intermittent headaches that had begun several months earlier
She had a
dry mouth but no difficulty swallowing.
Previously very active, she had become
homebound over a period of several months because of the leg weakness.
Weakness is a common symptom and can result from
dysfunction of either the central nervous system (brain or spinal cord) or the peripheral nervous system (anterior horn cell, nerve, neuromuscular junction, or muscle).
Bilateral symmetric weakness of the legs can also result from problems with either
the central or the peripheral nervous system.
A key question is whether the
arms are affected.
If the arms are spared,
a thoracic spinal cord lesion is most likely.
Peripheral nervous system dysfunction affecting the nerves, muscles, or neuromuscular junction can also cause
leg weakness; however, it is unusual for the diffuse processes that cause weakness in the muscles or neuromuscular junction to spare the arms.
The history of headaches, anxiety, depression, and memory difficulties in this patient indicates that the
brain is involved; because only rare midline brain lesions would affect the innervation of the legs bilaterally, these findings probably reflect a multifocal process.
Finally, dry mouth is nonspecific but can tie into
leg weakness in many ways — for example, through the myelopathy that may accompany
- Sjögren’s syndrome and the
- autonomic dysfunction of the Lambert–Eaton myasthenic syndrome.
The patient had a history of
breast cancer that had been diagnosed 20 years earlier.
Treatment included
lumpectomy and radiation therapy, and there had been no evidence of recurrence.
She also had
- gastroesophageal reflux disease,
- hypertension, and the
- irritable bowel syndrome.
Her medications included
aspirin, lisinopril, ranitidine, and paroxetine.
She had
smoked one pack of cigarettes daily for 45 years.
Her father had
chronic obstructive pulmonary disease,
her mother had
neuromyelitis optica,
one sibling had
scleroderma, and
another sibling had
head and neck cancer.
The history of
breast cancer puts the patient at risk for recurrence, which can take the form of parenchymal lesions in the brain and spinal cord or carcinomatous meningitis.
Her smoking history and family history of head and neck cancer put her
at risk for a new, smoking-related cancer.
Paraneoplastic syndromes, as well as primary or metastatic cancers, can affect
the central or peripheral nervous system.
Paraneoplastic antibodies produced by typically small tumors can target either
neuronal cell-surface and synaptic antigens or intracellular antigens, leading to neurologic dysfunction.
Breast cancer and lung cancer in particular have been associated with a
wide range of neurologic paraneoplastic syndromes.
The family history of neuromyelitis optica and scleroderma places the patient at risk for
autoimmune conditions, many of which, such as systemic lupus erythematosus and Sjögren’s syndrome, can be manifested as leg weakness.
The patient was
afebrile.
Her heart rate was
84 beats per minute, her blood pressure was 160/74 mm Hg, her respiratory rate was 12 breaths per minute, and her oxygen saturation was 97% while she was breathing ambient air.
She had moderate
weakness in hip flexion and in knee flexion and extension bilaterally.
Strength in the feet, ankles, hands, and arms was
normal.
Knee and ankle reflexes were
normal, and plantar reflexes were flexor bilaterally.
Sensation of light touch and vibratory sensation were
normal throughout her body.
Her casual gait was
normal, but she had difficulty with a tandem gait and difficulty standing on her heels or toes.
Cranial-nerve function was
normal
The pattern of symmetric, proximal weakness without
reflex or sensory abnormalities probably points to a problem at the level of the muscle or neuromuscular junction.
Inflammatory diseases of the muscles include
polymyositis, dermatomyositis, and inclusion-body myositis; however, the presence of autonomic dysfunction (i.e., dry mouth) and neuropsychiatric features would be atypical.
Because most muscle disorders lead to breakdown of the muscles, measurement of the
serum creatine kinase level would be useful.
Although myasthenia gravis is by far the most common neuromuscular-junction disorder, the absence of
oculobulbar features makes this diagnosis highly unlikely.
The combination of proximal muscle weakness, autonomic dysfunction, and absence of eye findings is most consistent with a diagnosis of the
Lambert–Eaton myasthenic syndrome.
In more than 90% of patients with this syndrome,
autonomic dysfunction develops during the course of the disease, usually within the first 3 months after symptom onset.
To further evaluate these possible diagnoses, the patient should be assessed for the presence of
fluctuation, or changes in muscle strength over time, which is a key discriminator between disorders of the muscles and disorders of the neuromuscular junction.
This can be tested by examining sustained power in an affected muscle over a period of
10 to 30 seconds or by observing changes in power after exercise of a limb.
Patients with myasthenia gravis may have fluctuation with
fatigability, whereas slight increases in strength can be seen in patients with the Lambert–Eaton myasthenic syndrome.
Electromyography and nerve-conduction studies can definitively
localize weakness to either the muscle or the neuromuscular junction and provide clues about the cause.
Repetitive-stimulation testing during nerve-conduction studies can be used to
classify disorders of the neuromuscular junction as presynaptic, in which facilitation is seen (e.g., the Lambert–Eaton myasthenic syndrome), or postsynaptic, in which a decremental response is seen (e.g., myasthenia gravis).
