From 1984 to 1988, 11 of 120 patients (9%) with motor neuron disease (MND) had paraproteins detected by serum immunofixation electrophoresis (IFE), compared with 4 (3%) by cellulose acetate gels: 1 patient had progressive spinal muscular atrophy, 5 patients had amyotrophic lateral sclerosis (ALS), and 5 patients had ALS with probable upper motor neuron signs. Four of 5 patients (80%) with cerebrospinal fluid (CSF) protein content above 75 mg/dl had paraproteins, as did 6 of 30 with values above 50 mg/dl. Four of 14 patients with cerebrospinal oligoclonal bands (OCB) also had paraproteins. Two patients with ALS, CSF protein content above 75 mg/dl, and paraproteinemia had lymphoma. We conclude the following about patients with MND: high CSF protein content (especially above 75 mg/dl) or CSF OCB makes paraproteinemia more likely; some of these patients may have lymphoma; there is an inordinately high occurrence of paraproteinemia in MND; and IFE on agarose is more sensitive than electrophoresis on cellulose acetate in detecting paraproteins. Syndromes of paraproteinemia and high CSF protein are not restricted to the lower motor neuron but qualify as "ALS" with coexisting upper motor neuron signs.
We developed a new micro-scale procedure for determination of protein in cerebrospinal fluid and urine. The sample (50 µl) is mixed with a trichloroacetic acid—Ponceau S dye solution. The proteins, together with a proportional amount of dye, are precipitated and the red precipitate is dissolved in dilute sodium hydroxide solution, giving a violet-colored solution. This color, linearly proportional to the amount of protein present (up to 150 mg/dl), is measured spectrophotometrically at 560 nm. By varying the sample size alone, protein concentrations up to 1500 mg/dl can be measured. The detection limit for the method is 2 mg/dl of sample. Precipitation of the proteins is independent of temperature and albuminbinding compounds, and is not appreciably affected by the albumin—gamma globulin ratio.
We studied 9 patients with motor neuron disease and lymphoma. The following several observations have not been recognized in the past: (1) Motor neuron syndromes are associated with either Hodgkin's disease or non-Hodgkin's lymphoma. (2) The syndromes are not restricted to lower motor neuron disorders; 8 of 9 patients had definite or probable upper motor neuron signs as well, qualifying for the diagnosis of amyotrophic lateral sclerosis. Corticospinal tracts were affected in both postmortem examinations. (3) The combination of motor neuron disease and lymphoma is often accompanied by paraproteinemia (3 of 7 patients studied), increased cerebrospinal fluid protein content (6 of 9 patients), and cerebrospinal fluid oligoclonal bands (3 of 9 patients). (4) In 2 patients, asymptomatic non-Hodgkin's lymphoma was found only because the discovery of paraproteinemia gave impetus to examine the bone marrow. (5) Patients with both upper and lower motor neuron signs (amyotrophic lateral sclerosis) may show physiological evidence of conduction block in peripheral nerves or autopsy abnormalities in peripheral nerves. The cause of this syndrome is not known. Both lymphoma and motor neuron disease could have a common cause, possibly a retroviral infection. The frequency of paraproteinemia suggests that an immunological disorder may play a role in the pathogenesis of the neurological disorder.
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