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Table 2: Comparison between patients and controls in DISCUSSION
scores of cognitive functions and depression
Variable Patients Controls P The results of this study indicate that patients with
(n = 20) (n = 20) mild/moderate MG may experience significant
MMSE 23.25 ± 2.35 27.56 ± 1.45 0.036 manifestations of cognitive impairment in the absence
SBST of disease activity and despite the short duration
Vocabulary 36.33 ± 5.45 50.45 ± 3.88 0.042
Comprehension 35.46 ± 9.07 49.76 ± 7.56 0.007 of illness. Patients with MG may experience poor
Total verbal reasoning 75.32 ± 8.85 96.82 ± 16.25 0.0001 performance in different cognitive tasks indicating
score central or brain involvement. These included deficits
Visual reasoning 36.63 ± 4.64 48.68 ± 5.04 0.0001
Total visual reasoning 68.43 ± 8.09 88.33 ± 14.70 0.0001 in verbal relations, comprehension, visual reasoning,
score pattern analysis, quantitation, bead memory, short‑term
Quantitative test 36.57 ± 6.54 45.30 ± 5.43 0.0001 memory and memory for sentences, digit forward,
Total quantitative 75.53 ± 8.67 96.65 ± 9.57 0.0001
reasoning score digit backward, mental control, logical memory, and
Bead memory 45.30 ± 7.28 60.50 ± 10.08 0.0001 associate learning. In the agreement with our findings,
Memory for sentences 44.72 ± 6.34 65.56 ± 8.57 0.0001 patients with MG commonly reported subjective
Total score for 85.65 ± 9.66 150.25 ± 25.26 0.0001
short‑term memory cognitive complaints. In patients with MG, several
Total score of SBST 289.56 ± 55.48 360.34 ± 50.04 0.0001 previous studies reported memory difficulties [17,18] and
IQ 78.53 ± 6.46 95.35 ± 8.73 0.0001
WMS‑R impaired performance on varieties of cognitive tests as
Digit forward 4.56 ± 1.01 6.64 ± 0.88 0.035 MMSE and memory tests, [19] the Boston Naming Test,
Digit backward 2.23 ± 0.25 5.58 ± 0.45 0.010 the Logical Memory and Design Reproduction portions
Mental control 3.57 ± 1.45 5.89 ± 1.06 0.042 of the WMS, Rey Auditory Verbal Learning Test, [17] and
Logical memory 10.65 ± 1.30 14.83 ± 2.45 0.007
Associate learning 8.52 ± 2.04 12.06 ± 2.24 0.005 measures of response fluency, information processing
Total scores of cognitive 76.54 ± 8.35 96.54 ± 6.28 0.0001 and verbal and visual learning. [20,21,47] In additions, the
testing (MMSE, SBST detected abnormalities in P300 component of ERPs
and WMS‑R)
Depression scores 20.64 ± 6.24 8.65 ± 3.55 0.0001 also suggest the central or brain involvement in MG.
Data are expressed as mean ± SD. SBST: stanford Binet subtests testing, In fact, abnormal evoked potential responses were
MMSE: mini‑mental state examination, WMS‑R: wechsler memory scale‑revised, noted in patients with MG. [48‑50] In contrast, several
SD: standard deviation, IQ: intelligence quotient
studies reported normal IQ, memory, attention and
motor performance and normal ERPs in MG. [25‑27] We
Table 3: Comparison between patients and controls in believe that such discrepancies could be explained
event‑related potentials
Variable Patients (n = 20) Controls (n = 20) P by differences in methodologies, small sample size,
P latency (ms) different lists of inclusion and exclusion criteria and
300
Right sided 250.00‑450.00 285.00‑353.00 ‑ lack of control for potential confounding variables.
350.80 ± 35.88 320.88 ± 25.75 0.010
Left sided 270.00‑450.00 250.00‑350.00 ‑ Several mechanisms have been hypothesized as
355.60 ± 33.08 325.45 ± 20.45 0.010
P amplitude (mv) etiologies of cognitive impairment in patients with MG.
300
Right sided 2.20‑20.25 6.88‑20.54 ‑ The central cholinergic deficiency due to the involvement
7.55 ± 2.45 12.45 ± 2.84 0.001 of the central nAChRs and central cholinergic pathways
Left sided 2.55‑18.09 6.80‑22.25 ‑
6.67 ± 3.23 12.63 ± 2.56 0.001 by the disease process of MG have been suggested as the
Data are expressed as range, mean ± SD. SD: standard deviation high likely mechanisms. [20,28‑30] This hypothesis is based
on the fact that there are structural identities between
Table 4: Pearson’s correlation (r and P value) between different muscle and neuronal nAChRs subunits with
total scores of cognitive testing and clinical variables, lab the possibility of cross‑reactivity between different
variables, depression scores and ERPs variables nAChRs antibodies. [51‑53] The hippocampus, a cerebral
Variables Total scores of cognitive structure highly involved in learning and memory,
testing (MMSE, SBST and has abundant cholinergic innervation and enriched
WMS‑R) in nAChRs that modulate synaptic plasticity via
r P mechanisms involved in long‑term potentiation. [54]
P latency ‑0.650 0.001
300
P amplitude 0.557 0.001 Few suggested that cognitive dysfunction co‑morbidity
300
Age ‑0.470 0.010 may be due to the immune responses driven by
Duration of illness ‑0.788 0.0001 muscle and neuronal nAChRs antibodies expressed
Depression scores ‑0.323 0.045
ERPs: event‑related potentials, MMSE: mini‑mental state examination, by cancer (e.g. thymoma) (i.e. paraneoplastic
SBST: stanford Binet subtests testing, WMS‑R: wechsler memory scale‑revised syndrome). [55,56] Others suggested that it might be a
nonspecific autoimmune response in presence or
total scores of cognitive testing (MMSE, SBIS and absence of tumor. [57] This it further supported by an
WMS‑R) and duration of illness (β = ‑0.305, P = 0.045). association of MG with other nonnervous system medical

144 Neuroimmunol Neuroinflammation | Volume 1 | Issue 3 | December 2014