Many neurological syndromes may accompany malignancy.
Clinical pictures include:
• Sensorimotor neuropathy
• Cerebellar syndrome
• Dementia and encephalopathy
• Myasthenic-myopathic syndrome (Eaton-Lambert syndrome)
• Progressive multifocal leucoencephalopathy
• Mononeuritis multiplex
• Cranial polyneuropathy
• MND variants
• Spastic paraparesis
The cause of most of these remains obscure. The clinical importance is that the neurological syndrome sometimes precedes clinical recognition of the neoplasm, which is often a small-cell carcinoma of the bronchus or a lymphoma. The neurological signs may recede if the tumour is resected or treated.
Fatiguability is the single most important feature. The proximal limb muscles, the extraocular muscles, and the muscles of mastication, speech and facial expression are those commonly affected in the early stages. Respiratory difficulties may occur.
Complex extraocular palsies, ptosis and a typical fluctuating proximal weakness are found. The reflexes are initially preserved but may be fatiguable Muscle wasting is sometimes seen late in the disease. been drug
The clinical picture of fluctuating weakness may bediagnostic but many cases are initially diagnosed as ‘hysterical’ .
Tensilon (edrophonium) test Edrophonium (an anticholinesterase) 10 mg i.v. is injected as a bolus after a test dose of 1-2 mg. Improvementin weakness occurs within seconds and lasts for 2-3 min when the test is positive. To be certain it is wise to have an observer present and to perform a control test using an injection of saline.
Occasionally the test itself causes bronchial constriction and syncope. It should not therefore be carried out where there are no facilities for resuscitation. Serum acetylcholine receptor antibodies These are present in 90% of cases of generalized myasthenia gravis. The antibodies are found in no other condition.
There is a characteristic decrement in the evoked muscle action potential following stimulation of the motor nerve. Other tests
Preliminary tests may show a mediastinal mass on chest X-ray that can be confirmed by mediastinal CT scanning. Routine peripheral blood studies are normal (the ESR is not raised). Autoantibodies to striated muscle, intrinsic factor or thyroid may be found. Rheumatoid factor and
antinuclear antibody tests may be positive. Muscle biopsy is usually not performed but ultrastructural abnormalities can be seen.