Journal of Babylon University/Pure and Applied Sciences/ No.(2)/ Vol.(21): 2013
Nerve Conduction Study and
Electromyographic Investigation in Newly
Diagnosed Patients with Thyroid Dysfunction
Farah Nabil Abbas
Najeeb Hassen
Suhair Nadhm Mahmoud
Ihsan Mohammad Ajeena
Abstract
Background
Thyroid dysfunction is associated with characteristic symptoms and signs and
functional alterations in many organs and systems. Central and peripheral nervous
systems affection may provide the major presenting symptoms.
The purpose of this study is to evaluate objectively the functional changes in the
peripheral nervous system and muscles by different electrophysiological parameters in
recently diagnosed thyroid disease patients before any treatment and to determine the
frequencies of these changes.
Materials and Methods: 131 subjects were included in this study. Of them, 58 with
hypothyroidism, 31 with hyperthyroidism and 42 were normal, as control group, all of
them were free from other disease which could affect peripheral or central nervous
system.
The electrophysiological tests were done at the neurophysiology unit of Mirjan
Teaching hospital in Babylon City, during the period Nov/2009-March/2011.
Nerve conduction studies and electromyography, were performed for the patients
and control in parallel.
Results: The involvement of the sensory fibers are more than that of the motor fibers
and the affection of the lower limbs nerve fibers are worse than that of the upper
limbs in both hypo and hyperthyroid patients when compared with the control group.
The most commonly involved nerves are the sural nerve and median nerve sensory
fibers (43.1%, 39.6% in hypothyroid patients and 32.2%,32.2% in hyperthyroid
patients respectively, while senseromotor neuropathy is the less common one (13.8%,
3.2%).
In electromyographic studies, amplitude and duration of the motor unit potentials in
deltoid and abductor pollicis brevis muscles were performed, and myopathic changes
mainly in the proximal muscles of the hypothyroid patients were recorded.
Conclusion
Results of this study indicates the early affection of the peripheral nervous system
and muscles in the newly diagnosed thyroid patients. Therefore, we suggest
performing electrophysiological studies in those patients, even in the asymptomatic
ones, early in the course of disease in order to detect these changes.
‫الخالصة‬
‫يرافق اضطراب الغدة الدرقية مجموعة من األعراض و العالمات السريرية مع تغيير في وظائف و أجهزة الجسم‬
.‫و يعتبر الجهازين العصبي المركزي و المحيطي من أكثر األجهزة تأث اًر بهذا االضطراب‬
‫الهدف من هذه الدراسة هو فحص التغيرات الكهروفسلجية للجهاز العصبي المحيطي مع العضالت للمشخصين‬
.‫حديثاً من مرضى اضطراب الغدة الدرقية قبل إعطاء العالج‬
626
‫شملت هذه الدراسة ‪ 131‬شخصاً‪ ,‬منهم ‪ 58 :‬مريضاً مصاباً بنقصان إفراز الغدة الدرقية و كذلك ‪ 31‬مريضاً‬
‫مصاباً بزيادة إفراز الغدة الدرقية و كذلك ‪ 42‬شخصاً طبيعياً بعد استثناء األمراض األخرى التي من الممكن إن تؤثر على‬
‫الجهاز العصبي و المركزي‪.‬‬
‫الفحوصات الكهروفسلجية تم إجراؤها في وحدة الفسلجة العصبية في مستشفى مرجان التعليمي في مدينة بابل للفترة‬
‫من تشرين الثاني ‪ 2009‬إلى آذار ‪.2011‬‬
‫شملت االستقصاءات الكهروفسلجية تخطيط األعصاب المحيطية الكهربائي‪ ,‬تخطيط العضالت الكهربائي للمرضى‬
‫و األشخاص الطبيعيين على ٍ‬
‫حد سواء‪.‬‬
‫شمل تخطيط األعصاب المحيطية كفاءة األعصاب الحسية (لكل من العصب الناصف"الوسطي"‪ ,‬العصب الزندي و‬
‫العصب الربلي) و األعصاب الحركية و كذلك دراسة موجة –ف (لكل من العصب الناصف " الوسطي"‪ ,‬العصب الزندي و‬
‫العصب الظنبوبي الخلفي)‪.‬‬
‫ان تقييم األعصاب الحسية يظهر تدهو اًر ملحوظاً في كفاءتها أكثر من األعصاب الحركية و أعصاب األطراف‬
‫السفلى أكثر من العليا و يعد العصب الوسطي و العصب الربلي من أكثر األعصاب تأث اًر (‪ )%43.1, 39.6‬لمرضى‬
‫نقصان افراز الغدة الدرقية و (‪ )% 32.2 , 32.2‬لمرضى زيادة إفراز الغدة الدرقية بالتعاقب بينما اعتالل األعصاب‬
‫الحسية الحركية شمل األقلية من النسب ‪.% 13.8‬‬
‫في تخطيط العضلة الكهربائي تم استقصاء سعة الموجة مع مدة كمون الفعل للوحدة الحركية للعضلتين (العضلة‬
‫الذالية و العضلة القصيرة المبعدة إلبهام اليد) و لوحظ وجود اعتالل في العضلة الذالية للمرضى المصابين بنقص إفراز‬
‫الغدة الدرقية‪.‬‬
‫لوحظ في هذه الدراسة التأثر المبكر لالعصاب المحيطية و العضالت لمرضى اضطراب الغدة الدرقية المشخصين‬
‫حديثاً‪ ,‬لذا نوصي بإجراء الفحوصات الكهروفسلجية لهؤالء المرضى في وقت مبكر من ظهور المرض قبل ظهور األعراض‬
‫المصاحبة له لتحديد إصابة األجهزة العصبية‪.‬‬
‫*اعتمد في تعريب المصطلحات العلمية على ‪:‬‬
‫‪ -1‬اطلس التشريح العصبي‪ .‬األستاذ الدكتور محمد توفيق الرخاوي‪ .‬جمهورية مصر العربية‪ -‬الطبعة األولى‬
‫‪ 2000‬م‪.‬‬
‫‪ -2‬المعجم الطبي الموحد – انكليزي – عربي‪ .‬رئيس التحرير د‪ .‬محمود الجليلي – الطبعة الثانية’ ‪ 1978‬م‪,‬‬
‫مطبعة المجمع العلمي العراقي‪.‬‬
‫‪ – 3‬الموجز المصور لفحص الجهاز العصبي‪ .‬ترجمة د‪ .‬عبد الهادي الخليلي – بغداد – ‪ 1992‬م‪ ,‬د‪.‬موريس‬
‫فان الن و د‪ .‬روبرت روزنسكي‪.‬‬
‫‪Introduction‬‬
‫‪Endocrine diseases have protean manifestations and present with a wide variety of‬‬
‫‪symptoms pertaining to different body systems. This results, at times, in diagnostic delays‬‬
‫‪and dilemmas; hence it is important for the clinician to be familiar with the neurological‬‬
‫‪manifestations of endocrinopathies. Amongst various endocrine disorders, thyroid diseases‬‬
‫‪are common in clinical practice (Redmond, 2002; Khadilkar, 2010).‬‬
‫‪Thyroid hormones are involved in many functions of the central and peripheral‬‬
‫‪nervous system and as a result both hyperthyroidism and hypothyroidism may cause‬‬
‫‪various neurological signs and symptoms(Abend & Tyler, 1995; Khedr et al., 2000).‬‬
‫‪The prevalence of neuromusculer disorders related to thyroid dysfunction has been‬‬
‫‪reported to be between 20-80% (Abend & Tyler, 1995; Duyff et al., 2000).‬‬
‫‪More than one area may be affected but the brunt tends to be borne by some organ‬‬
‫‪systems and this organ selectivity differs from one individual to another. It is also‬‬
‫‪627‬‬
Journal of Babylon University/Pure and Applied Sciences/ No.(2)/ Vol.(21): 2013
important to recognize that the neurological manifestations may be the presenting
features and the other systems may be normal, to a large extent, at the time of
presentation(Kissel & Mendell, 1992).
Two different types of peripheral nerve abnormalities are associated with
established hypothyroidism. Although the most common disorders are the entrapment
neuropathies, especially carpal tunnel syndrome (CTS), sensorimotor
polyneuropathies can also be seen in these patients(Nemni et al., 1987; Palumbo et
al., 2000). The severity of the neuromuscular signs and symptoms are known to be
related to the duration and degree of hormonal deficiency and clinical,
electrophysiological and morphological improvement following hormone replacement
therapy is typical(Nemni et al., 1987; Latov, 1995; Palumbo et al., 2000) and
(Amato, 2002). Hyperthyroidism is less commonly associated with neuromuscular
disorders and polyneuropathy is a relatively rare complication of hyperthyroidism(Klein &
Levey, 1984; Nemni et al., 1987; Tonner & Schlechte, 1993) and (Duyff et al., 2000).
Materials and Methods
131 subjects were included in this study. Of them, 58 with hypothyroidism, 31 with
hyperthyroidism and 42 were normal, as control group, all of them were free from
other disease which could affect peripheral or central nervous system.
The electrophysiological tests were done at the neurophysiology unit of Mirjan
Teaching hospital in Babylon City, during the period Nov/2009-March/2011.
Nerve conduction studies and electromyography, were performed for the patients
and control in parallel.
Nicolet NCS-EMG machine was used for all the built-in two isolated stimulators
with separate jacks.
For both the sensory and motor fibers measurements, the skin was adequately
prepared before the application of the stimulating and recording electrodes to ensure
good contact between these electrodes and the skin and to avoid any shock artifacts.
This preparation included cleaning the skin by spirit and then drying it. Also, when
calloused skin is present, it was brushed by a cleaning gel or even abraded gently with
a fine sandpaper.
The electrodes were also prepared to ensure good conduction with subjects skin and
to decrease skin impedance. These preparations included the soaking of the grounding
electrodes, sensory recording electrodes, and the felt tips of the stimulating electrodes
in normal saline. Also they included the application of an electrode gel over the
recording motor electrodes before being applied to the skin(Ludin, 1980; Kimura,
2001).
For both sensory and motor action potential recordings, the active recording
electrode is placed proximal to the reference one, and regarding the stimulating
electrodes, the anode is placed proximal to the cathode.
Distal sensory latency, sensorial nerve action potential amplitude, nerve conduction
velocity, were recorded in the sensorial nerve conduction studies of median, ulnar
and sural nerves, distal motor latency, compound muscle potential amplitude, nerve
conduction velocity, minimum F- latency were recorded in the motor nerve
conduction studies, of median, ulnar and posterior tibial nerves.
The muscles examined were the right deltoid and abductor polices brevis of all
subjects. Using surface anatomy the muscle belly was identified and after disinfecting
the skin overlying the muscle to be examined, implementation was performed by the
needle electrode. The certainty of the electrode being inserted into the muscle is made
by listening to the peculiar sound produced by the action potentials through the loud
speaker.
628
The potentials appear on the screen of the oscilloscope representing the insertion
activity due to mechanical stimulation of the muscle fibers by the advancing
electrode.
The following parameters were specifically looked for in the EMG examination of
the these muscles:
1. spontaneous activity in relaxed muscle.
2. Twenty different motor unit potentials of each muscle were recorded and their
average duration and amplitude were obtained.
3. The pattern of electrical activity during maximum contraction.
Statistical analysis
Using the statistical Package for the social Sciences(SPSS), the arithmetic mean and
standard deviation of distribution of each of the parameters were calculated for all of
the subjects.
The One Way ANOVA test was used to get the significance level
(p-value) for all the patients parameters tested after being compared with that of the
control group.
Chi- square test was used to see the percentage and the significant level of the
categorical variables.
The T-test also used to get the mean ± SD of any parameter.
A p-value equal to or less than 0.05 and 0.001 is considered to be significant and
highly significant, respectively(Daniel, 1983).
Results
The characteristics of the eighty nine patients with thyroid dysfunction regarding
their age, gender and their temperature were compared with control group (forty two
subjects). These results and their level of significance were shown in table (1).
Table 1- The characteristics of the thyroid dysfunction patients and the control
group
Subject
Character
No.
Age (no. and
percent)
Gender
Male
(no. and Female
percent)
Temp. C°
Control
group
42
30.55±4.45
Hypothyroid
patients
58
32.05±6.45
Hyperthyroid
patients
31
34.97±5.05 NS
16(38.1%)
26(61.9%)
16(24.6%)
42(72.4%)
11(35.5%) NS
20(64.5 %) NS
36.89±0.27
36.86±0.24
36.90±0.28
Temp. =Temperature
NS = Non significance = p – value > 0.05
Nerve Conduction Studies:
629
NS
Journal of Babylon University/Pure and Applied Sciences/ No.(2)/ Vol.(21): 2013
Table 2-The results of median nerve sensory and motor conduction parameters
within hypothyroid, hyperthyroid patients and control group.
Control
Hypothyroid
patients
Hyperthyroid
patients
2.33 ± 0.51
2.80 ± 0.51 **
2.70 ± 0.51 *
33.37±10.97
23.60 ±11.63 **
28.06 ± 8.88 *
50.55 ± 7.21
44.37 ± 10.56 *
46.38 ± 6.84 *
2.91 ± 0.58
3.49 ± 1.23 *
3.22 ± 0.83
12.38 ± 3.08
10.14 ± 3.27 *
11.70 ±5.14
64.98±5.75
60.31±6.33 **
62.25±689
24.29±2.39
26.18 ± 2.87 *
25.64±3.19 *
Parameter
DSL.
(m.sec)
(mean ± SD)
SensoryAmp(µvolt)
(mean ± SD)
Sensory CV(m/sec)
(mean ± SD)
DML(m.sec)
(mean±SD)
MotorAmp (m.volt)
(mean±SD)
Motor CV
(m/sec)
(mean±SD)
F-wave
* significant = p-value < 0.05
** Highly significant = p-value < 0.001
Table 3- The results of ulnar nerve sensory and motor conduction parameters
within hypothyroid, hyperthyroid patients and control group.
Control
Hypothyroid
patients
Hyperthyroid
patients
DSL.
(m.sec)
(mean ± SD)
1.66 ± 0.28
1.71 ± 0.58
1.84 ± 0.31
SensoryAmp(µvolt)
(mean ± SD)
31.47±12.49
27. 34 ± 9.44
27.06 ± 10.61
Sensory CV(m/sec)
(mean ± SD)
55.14 ± 3.51
53.50 ± 4.34 *
53.32 ± 2.95 *
DML(m.sec)
(mean±SD)
2.10 ± 0.28
2.16 ± 0.35
2.06 ± 0.17
MotorAmp (m.volt)
(mean±SD)
5.96 ± 1.12
5.79 ± 1.16
5.87 ± 0.92
Motor CV
(m/sec) (mean±SD)
60.23 ± 6.00
58.31 ± 5.40
58.40 ± 5.47
F-wave
23.54 ± 0.80
24.06 ± 1.93
23.77 ± 1.74
Parameter
* significant = p-value < 0.05
630
Table 4-The results of tibial nerve motor conduction parameters within
hypothyroid, hyperthyroid patients and control group.
Parameter
DML(m.sec)
(mean±SD)
MotorAmp
(m.volt)
(mean±SD)
Motor CV
(m/sec)
(mean±SD)
F-wave
Control
Hypothyroid
patients
Hyperthyroid
patients
3.06 ± 0.26
3.15 ± 0.36
3.12 ± 0.34
5.02±1.17
5.25 ±1.75
5.37 ±1.63
51.78±7.92
49.12±8.82
50.00±7.07
46.11±1.53
47.06.±2.98
47.00.±1.71
Table 5-The results of sural nerve conduction parameters within hypothyroid,
hyperthyroid patients and control group.
Parameter
DSL.
(m.sec)
(mean ± SD)
SensoryAmp(µvol
t)
(mean ± SD)
Sensory
CV(m/sec)
(mean ± SD)
Control
Hypothyroid
patients
Hyperthyroid
patients
1.76 ± 1.44
2.39 ± 0.49 **
2.35 ± 0.48 **
23.85±4..91
17.63 ± 7.8 **
16.58 ± 7.08 **
46.50 ± 3.39
41.39 ± 9.05 **
43.70 ± 7.85
** Highly significant = p-value < 0.001
Electromyographic Findings:
The amplitude and duration of the motor unit potentials in both deltoid and abducter
pollicis brevis (APB) muscles within hypothyroid, hyperthyroid patients and control
group were examined and are shown in tables 6.
The deltoid as a proximal muscle and the APB as a distal one.
631
Journal of Babylon University/Pure and Applied Sciences/ No.(2)/ Vol.(21): 2013
Table 6- Some parameters of motor unit potentials of deltoid and APB in thyroid
dysfunction patients and in the control group.
Control
Hypothyroid
patients
Hyperthyroid
patients
745 ± 181
560 ± 209 **
727 ± 212
742±174
725 ± 179
735 ± 181
Deltoid duration
(m sec)
(mean ± SD)
8.95 ± 1.61
8.10 ± 2.82
8.64 ± 1.89
APB duration
(m. sec)
(mean ± SD)
8.89±1.94
8.25 ± 2.17
8.80 ± 1.94
Parameter
Deltoid Amp
(µv)
(mean ± SD)
APB Amp
(µv)
(mean ± SD)
** Highly significant = p-value < 0.001
Most sensory and motor parameters of some peripheral nerves were measured and
their results shows different significant levels from the control group, and these results
are discussed below:
Common neurophysiological abnormalities in thyroid dysfunction:
Table -7 Electrophysiological abnormalities in hypothyroid and hyperthyroid
patients.
Findings
Hypothyroid Hyperthyroid
CTS
23(39.6%))
10(32.2%)
Sural mononeuropathy
25(43.1%)
10(32.2%)
Sensory neuropathy
26(44.8%)
11(35.5%)
Senseromotor polyneuropathy
8(13.8%)
1(3.2%)
Discussion
The DSL of the median nerve was prolonged and the amplitude was decreased in
hypothyroid and hyperthyroid patients (<0.001 and <0.05) respectively when
compared with the control group, findings that are consistent with that of Klein and
Levey (1984) and Khedr et al (2000).
The SCV of the median nerve in both hypothyroid and hyperthyroid patients was
significantly decreased when compared with the control group, these results agreed
with the results of other researchers(Begni et al., 1989; Brian & Bolton, 2002).
The DML, amplitude, MCV and F-wave of the median nerve in hypothyroid
patients was significantly changed when compared with the control group, these
results agreed with (Begni et al., 1989; Duyff et al., 2000) and (Brian & Bolton, 2002)
and disagreed with others (Misiunas et al., 1995; Ozata et al., 1996). While in
hyperthyroid patients the results were not significant, except the F-wave and this is
consistent with findings of Feibel and Campa (1976) and Ozata, et al (1995).
632
There were no significant alteration in parameters of the ulnar nerve in both
hypothyroid and hyperthyroid patients when compared with that of the control group,
except the SCV in hypothyroid and hyperthyroid patients that significantly decreased,
these results are in agreement with other researchers Klein and Levey (1984) who
found abnormal conductive parameters in ulnar nerve.
The DSL of the sural nerve was prolonged, the amplitude was decreased and the
SCV was also decreased (<0.001) in both hypothyroid and hyperthyroid patients when
compared with the control group, these results agreed with many researchers
(Schwartz et al., 1983; nemni et al. 1987) and (Khedr et al., 2000).
The conductive parameters of the tibial nerve (DML, MCV and F-wave) in
hypothyroid and hyperthyroid patients statistically were not significant when
compared with the control group, these results are the same results(Begni et al., 1989;
; Tietgens & Leinung, 1995) and (Khedr e al., 2000).
In normal subjects, EMG study revealed that all motor unit potentials had normal
shape of the potential. The parameters of the motor unit potentials and the interference
pattern in all of them were perfectly normal. This is because neither insertion activity
of long duration nor spontaneous muscle activity were noticed. This is in complete
agreement with previous findings by other researchers(Ludin, 1980; Landau et al.,
2003). Spontaneous activity was absent in both proximal and distal muscle, this does
not agree with Scarpalezos et al (1973) and Shasha (1989) who reported these
potentials in the APB in which the age of their patients were above 45 years, while in
our study it was below 45 years, because of the chronicity of the disease affecting the
nerve supplying the APB leading to partial denervation.
However it was difficult to find absolute values for average amplitudes of the motor
units in the literatures, which is probably due to the variability of the amplitudes
encountered during recording that is why we completely relay on the comparison
between the patient and the control group.
In the present study the mean amplitude of the deltoid in hypothyroid patients was
significantly lower when compared with mean amplitude of this muscle in control
subjects. This finding is in agreement with previous researchers who were able to
demonstrate reduced amplitude of the motor unit potentials in proximal muscles of
hypothyroid patients(Shasha, 1989; Kissel et al., 1992) and (Hilton-Jones et al.,
1995). This finding of reduced amplitude of motor unit potentials can be considered
as one of the evidences pointing out to myopathy, because in myopathy there is loss
of muscle fibers and reduced fiber density. This suggests that hypothyroidism affects
not only peripheral nerves but also the skeletal muscles, mainly the proximal ones.
Regarding the duration of the motor unit there were no significant correlation in
hypothyroid patients when compared with the control group.
In the present study there were no significant EMG findings in hyperthyroid
patients by comparing them with the control subjects these findings agreed with
(Ozata et al., 996) and disagreed with others (Satoyoshi et al., 1963; Duyff et al.,
2000).
It is known that thyroid hormones are involved in many processes and functions of
the nervous system(Delongs & Adams, 1991). The severity of neuromuscular
symptoms and signs correlates well with the degree and duration of hormonal
imbalance(Torres & Moxley , 1990).
Our study shows that the hormonal and metabolic changes which are responsible
for the electrophysiological changes may occur early in the disease course before the
diagnosis of the thyroid disease.
633
Journal of Babylon University/Pure and Applied Sciences/ No.(2)/ Vol.(21): 2013
The metabolic alteration caused by hormonal imbalance affects the Schwann cell,
inducing demyelination that could be segmental. Primary axonal degeneration has
also been shown electrophysiologically and affected initially, but later structural
alterations may occur(Schwartz et al., 1983; Brian & Bolton, 2002), Since the distal
and sensory nerves are affected earlier (Yuksel et al., 2007), the most commonly
involved nerves are the sural nerve and median nerve sensory fibers. There is 25 (43.1
%) hypothyroid patients presented with sural mononeuropathy.
Hypothyroidism slows metabolism, leading to fluid retention and swollen tissues
that can exert pressure on peripheral nerves.
CTS is caused by the deposition of mucinous material in the tissue surrounding the
median nerve combined with hypothyroidism induced demyelinization (Nemni et al.,
1987; Schwarts et al., 1983; Khedr et al., 2000). The incidence of CTS varies and was
reported in 5-92% of hypothyroid patients(Torres & Moxley , 1990; Tietgens &
Leinung, 1995; Khedr et al., 2000; Yuksel et al., 2007) and concluded that thyroid
function tests were needed in all patients with carpal tunnel syndrome. In 1961,
Nickel et al. suggested that the mucinous infiltrates found in the peripheral nerves
could interfere mechanically with the metabolic exchange of nutrients and catabolic
products to and from the neuron resulting in entrapment neuropathy. Some
investigators (Pollard et al., 1982) found morphological evidence of primary axonal
degeneration. This could be explained by the energy deficit present in
hypothyroidism, leading to decreased oxidation and the glycogen deposits due to its
decreased degradation. In hypothyroidism, the ATP deficiency and reduced activity of
the ATP enzyme induce a decrease in Na+-K+ pump activity, with subsequent
alterations of pump-dependent axonal transport
which in turn leads to axonal neuropathy. This was supported by the study of
Sidenius et al. (1987) which demonstrated a reduced axonal velocity of slow
component in sciatic nerves of hypothyroid rats, which is suggested to lead to axonal
degeneration and peripheral neuropathy.
Our findings are compatible with other researchers. In this study 23(39.6%) of
hypothyroid patients had CTS.
Sensory neuropathy found in 26 (44.8%) of hypothyroid patients, while
Senseromotor polyneuropathy found in 8(13.8%) of hypothyroid patients.
The prevalence of neuropathy in hyperthyroidism is lower, the mechanism is
unknown (Tietgens & Leinung, 1995; Khedr et al., 2000). It has been suggested that
in severe thyrotoxicosis peripheral nerves are affected as well as dorsal root ganglion
and anterior horn cells. In a study involving 141 recently diagnosed untreated thyroid
disease patients, 20% of the hyperthyroid patients were reported to have an axonal
sensorimotor polyneuropathy (Sozay et al., 1994; Duyff et al., 2000; Cakir et al.,
2003).
In this study there is 10(32.2%) hyperthyroid patients presented with sural
mononeuropathy similar with the literature, sural nerve was the most commonly
involved nerve in this group of patients, while 10(32.2%) of them had CTS.
Senseromotor polyneuropathy found in 1(3.2%) of hyperthyroid patients.
Conclusion
1.
The involvement of the sensory fibers are more than that of the motor fibers and
the affection of the lower limbs nerve fibers are worse than that of the upper
limbs in both hypo and hyperthyroid patients. Furthemore, the sural
mononeuropathy and CTS represent the most common abnormalities in thyroid
disease patients.
634
2.
The underlying mechanism is mixed axonal and segmental demyelination,
however, demyelination is more common in both hypo and hyperthyroid
patients.
3. The prevalence of neuropathy in hyperthyroidism is lower than that in
hyperthyroidism.
4. The hormonal and metabolic changes which are responsible for the
electrophysiological changes may occur early in the disease course and can
cause symptoms before the diagnosis of the thyroid disease.
5. There were myopathic changes mainly in the proximal muscles of the
hypothyroid patients.
Results of this study indicates the early affection of the peripheral nervous system
and muscles in the newly diagnosed thyroid patients. Therefore, we suggest
performing electrophysiological studies in those patients, even in the asymptomatic
ones, early in the course of disease in order to detect these changes.
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