Academic journal article South African Journal of Psychiatry

Neuropsychiatric Symptoms in Patients with Thymoma-Associated and Non-Thymoma Myasthenia Gravis

Academic journal article South African Journal of Psychiatry

Neuropsychiatric Symptoms in Patients with Thymoma-Associated and Non-Thymoma Myasthenia Gravis

Article excerpt

Myasthenia gravis (MG) is characterised by muscle fatigability, which may be chronic and debilitating. [1] In patients who are positive for acetylcholine receptor antibodies, 10-15% have a thymoma. Thymomas are removed surgically, but the associated MG usually persists independently. Patients with thymoma-associated MG often have more severe disease than non-thymoma-associated patients, and may have additional non-motor symptoms and frequently require longterm treatment.[2] Psychiatric symptoms have been reported in MG patients,[3,4] although little is known about their frequency or their relation to thymoma MG. The only published report documents three cases of psychosis in which psychotic symptoms persisted despite thymectomy.[5]

We hypothesised that a patient with thymoma-associated MG will display a higher frequency of neuropsychiatric symptoms than patients with no thymoma. Here we report the findings of a pilot study in which both thymoma and non-thymoma MG patients were assessed using several neuropsychiatric questionnaires by investigators who were blind to thymoma status.


A cross-sectional study was done of 30 consecutive thymoma and nonthymoma MG patients attending a clinic at Groote Schuur Hospital, Cape Town, South Africa, over a 6-month period in 2010. Written informed consent was obtained and the University of Cape Town Health Sciences Human Research Ethics Committee approved the study.

Study population

All participants had MG and followed a standard treatment protocol that has been described elsewhere. [1] Patients with thymoma MG were stabilised on immunosuppressive therapy and a thymectomy was done at the earliest possible opportunity. Thymectomies are offered to patients with moderately severe generalised seropositive MG (<45 years), even in the absence of thymoma.

Interviews and tools

Interviews were done on the day of patients' clinic visit by a psychiatrist, blinded to thymic status. Assessments included the following: 16-item self-reported Flanagan Quality of Life (QOL) scale, the Beck Depression Inventory second version (BDI-II), Young Mania Rating Scale (YMRS), the Hamilton Anxiety Rating Scale (HAM-A), and the Brief Psychiatric Rating Scale (BPRS) (Table 1). We defined suicidal behaviour as current suicidal ideation or one or more previous suicide attempts.

Demographic data and psychiatric history were also obtained during the interview. The quantified MG score, recent thyroid studies, comorbid conditions and current treatment were subsequently obtained by folder review. Age at symptom onset, age at diagnosis and thymic histology were obtained from an MG database. [1] Participants were referred for further psychiatric management if indicated.

Statistical analysis

Data are presented as means and standard deviations (SDs), although skewed and ordinal data are presented as medians and interquartile ranges (IQRs). The Student t-test or Mann-Whitney U-test was used as appropriate and the Spearman rank-order correlation coefficient for ordinal data. Fisher's exact test was used for categorical data. A p-value (two-tailed) <0.05 was considered significant (Statistica 10 (Statsoft)).


Of the participants, 21 (70%) had non-thymoma MG and 9 (30%) had thymoma MG. Age and gender distributions, duration of MG disease and symptoms before diagnosis, as well as distribution of MG symptoms and disease severity between the two groups, were similar. As expected, the quantified MG scores correlated with prednisone dosing (rs = 0.39, p = 0.034). Although all patients were receiving steroid-sparing agents, at least two-thirds of both groups were also on prednisone (76%, non-thymoma MG; 66%, thymoma MG, p = 0.76). The average dose of prednisone was similar in the two groups (nonthymoma MG 16.3 mg/day; thymoma MG 17.2 mg/day, p = 0.86). Eight of nine subjects with thymoma MG had already undergone thymectomy. …

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