Case Index

PATIENT CASE STUDIES
Case 4 2/18 Disorders of the motor system


Case discussion

This 41 year old female presented with a insidious onset of progressive weakness and dysphagia over 4 months. At presentation she was unable to work and had difficulty walking upstairs. She had difficulty swallowing solids including meat and bread. She did not have extremity numbness, muscle tenderness, joint pains, incontinence, diplopia, anorexia, weight loss or rashes.

On examination general medical examination was unremarkable. Mental status was normal. Cranial nerve examination revealed weakness of neck flexion with good neck extension but was otherwise normal. Specifically extraocular movements were full, there was no ptosis and orbicularis oculi and facial strength were normal. Motor examination showed weakness of biceps, triceps, arm abductors, hip flexors, quadriceps. DTRs were 2+ and symmetric. Plantars were flexor. Sensory testing was normal. Cerebellar testing revealed dysmetria in proportion to weakness. There was full range of joint movements without joint tenderness or swelling.

  1. Summarize the Case in 1-2 sentences.

    2. This is a 41-year-old woman presenting with a 4 month history of progressive painless weakness, dysphagia, and proximal muscle weakness of all 4 limbs and neck with no sensory changes, full extraocular movements, no upper motor neuron signs, and no dermatologic findings.

    good

  2. Discuss lesion localization on the basis of the physical examination.

    3. muscle (weakness with no evidence of fatiguability or muscle wasting, normal DTRs, no UMN signs). The neck weakness, dysphagia, and dysmetria are manifestations of the muscle weakness.

    why is the dysmetria suggestive of muscle weakness?

  3. Discuss underlying pathogenesis on the basis of clinical course.

    4. The subacute, progressive course is consistent with inflammation, neoplasia, or a metabolic disorder

    good

  4. Indicate one likely clinical diagnosis. List (or classify) alternative diagnoses.

    5. Polymyositis

    good

    Other possibilities: (Lindsay & Bone, 456ff) degenerative diseases: muscular dystrophy
    inflammatory muscle diseases: dematomyositis, inclusion body myositis, SLE myopathy,
    infection (Coxsackie, echovirus), toxoplasmosis
    metabolic disorders: hypo/hyperthyroidism, hypo/hyperkalemia, hypo/hyperparathyroidism
    paraneoplastic syndromes: Lambert-Eaton, inflammatory myopathy of malignancy (over 10% of polymyositis cases)

    you should not include muscular dystrophies as these are degenerative disorders over years and are not included under question 3. otherwise good

  5. Indicate 2 ancillary tests that would assist in confirming or refuting the clinical diagnosis. Indicate the test results that would confirm the clinical diagnosis.

    6. serum CPK and aldolase elevations (but CPK can also be elevated in hypothyroid)

    muscle biopsy--definitive study, shows inflammatory infiltrate with lymphs, plasma cells, and other mononuclear cells, with resulting necrosis of muscle fibers.

    EMG--pattern of increased insertional activity, fibrillations, early recruitment, and low-amplitude action potentials. (Collins, p 27). The EMG has a sensitivity of about 85% for this disease (Adams, p 1406)

    i only ask for 2 tests

  6. Indicate complications of the disease and ancillary tests that would help evaluate them.

    7. About 10% of polymyositis and up to 60% of dermatomyositis patients harbor an associated neoplasm. An aggressive search for an occult tumor should be undertaken, esp. ovarian carcinoma. Neoplasia may not become evident until months after muscle symptoms. Also, about 15% of adults will have an associated autoimmune disorder (e.g. SLE, RA) which should be discovered and treated appropriately (ANA screen). Many patients also have cardiac involvement, which should be assessed by EKG. Pulmonary involvement with interstitial fibrosis is also common, and can be assessed with the anti-Jo-1 antibody screen. (Eur Respir J 1997 Dec;10(12):2907-12 Pulmonary fibrosis with predominant CD8 lymphocytic alveolitis and anti-Jo-1antibodies. Sauty A, et al) Even with treatment, most patients suffering from the idiopathic form are left with some degree of disability. Removal of associated neoplasm can bring about remission. Untreated, the disease can progress to respiratory failure, GI hemorrhage, and cardiac arrest.

    good. listing the complications makes them easier for me to read

  7. Discuss how the underlying pathophysiology is relevant in the management of this patient.

    8. The idiopathic form of this disease is caused by cellular-mediated autoimmune reaction to an unknown antigen of muscle fibers. Prednisone is started at 40-60mg, then tapered down while serum CPK levels are monitored. Long-term steroids are necessary in many cases. Methotrexate can be used in patients unable to tolerate steroids. Physical therapy and strength training programs have been proven effective for reducing disability due to this disease. (Br J Rheumatol 1998 Dec;37(12):1338-42 Benefit of 6 months long-term physical training in polymyositis/dermatomyositis patients. Wiesinger GF, et al)

    you should add what is known about targets eg. what is the Jo-1 antigen and similar antigens? also you should perhaps indicate that polymyositis can be a manifestation of different disease processes (as you say above, tumor, sle etc)

    perhaps you can also say pathogenesis in dermatomyositis is different from that of polymyositis