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eNeurologicalSci
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Pathological evidence of demyelination in the recurrent laryngeal, phrenic, and oculomotor
nerves in Charcot-Marie-Tooth disease 4F
A R T I C L E I N F O

A B S T R A C T

Keywords
Charcot-Marie-Tooth disease 4F
Periaxin
Vocal cord paresis
Recurrent laryngeal nerve
Phrenic nerve
Oculomotor nerve

We present pathology of the peripheral nerves of a patient with Adult-onset Charcot-Marie-Tooth disease 4F
caused by periaxin gene mutation p.D651N. The patient was a 72-year-old woman. She had hoarseness andunderwent continuous positive airway pressure therapy at night due to sleep apnea. The patient died abruptly.
Remarkable demyelination with tomacula formation was found in the phrenic nerve, vagal nerve, recurrent
laryngeal nerve, and oculomotor nerves. The cause of death could have been insufficient reactivity to theaspiration or sudden onset of bilateral vocal cord palsy. We must pay attention to respiratory function and cranial
nerve palsies in hereditary demyelinating neuropathies.

1. Introduction
Weakness and sensory disturbance of the limbs are well recognizedin Charcot-Marie-Tooth disease (CMT). However, its complications
affecting the respiratory function such as vocal cord paralysis are not soemphasized despite that impairment of these nerves is sometimes lifethreatening. One reason for that is that electrophysiological assess­ment and histological examination of cranial nerves is difficult orimpossible until death. Here, we describe a case of a female elderly
patient with CMT4F accompanied by periaxin gene mutation who diedsuddenly. The pathological findings of the peripheral nerves including
the oculomotor, recurrent laryngeal, vagal, and phrenic nerves arediscussed.
2. Case report
The patient was a 72-year-old woman. She was transferred from anursing home to our hospital due to cardiopulmonary arrest. Approxi­
mately 2 h after she took a lunch, she was discovered unconscious. A
small amount of food was observed in the trachea, indicating that she
vomited, but the airway was not obstructed. Intracranial bleeding andrupture of the aorta were ruled out after computed tomography.
Consolidation was found in her lower lung fields. Despite cardiopul­monary resuscitation, she died.
Her clinical symptoms before death had been described previously[1]. Briefly, she was the third child of healthy non-consanguineousparents. She had contracted infantile paralysis at the age of 18
months. She noticed a distal lower limbs weakness and sensory
impairment at the age of 30. She was diagnosed as having CharcotMarie-Tooth disease when she was 40 years old. At that time, she un­derwent a sural nerve biopsy. Although remarkable fiber loss ofmyelinated and unmyelinated nerve fibers was observed, typical onion
bulb formation was not found. She came to our hospital at the age of 65.
She was intellectually normal. She suffered from hoarseness with vocal
cord paralysis. A wheelchair was needed to move. Although she

underwent continuous positive airway pressure therapy at night due tosleep apnea, she never complained of dyspnea, dysarthria, or dysphagia
during daytime. There was no medical history of aspiration pneumonia
or diplopia. No compound muscle action potential or sensory nerve
action potential was derived in nerve conduction study of the median,ulnar, tibial, and sural nerves. Electromyography and neuroimaging
study for the peripheral nerve or nerve roots were not done. Under
informed consent, we performed genetic analysis. It revealed homozy­gous mis-sense mutation in periaxin gene (p.D651N, CMT4F).
Autopsy was performed according to her living will 44 h after her
death. Macroscopically, congestion of the lungs, liver, kidney, andspleen was found. Coronary arteries were patent. The brain weight was
1290 g. The spinal roots were enlarged remarkably. In the peripheral
nervous system, the oculomotor nerve adjacent to the midbrain, thephrenic and vagal nerves at the thoracic level, and the recurrent
laryngeal nerve were dissected out with other somatic nerves including
the anterior and posterior spinal nerve roots and the sciatic nerve. After
fixation with 2.5% glutaraldehyde and 2% paraformaldehyde, osmica­tion, and embedding in epoxy resin, these tissues were stained in tolu­
idine blue. Teased fiber technique was also performed.
In all nerves, myelinated nerve fiber loss and thinning of the myelin
were remarkable (Fig. 1A-F). Onion-bulb formation was observed in thesciatic, phrenic, vagal nerves, and the anterior and posterior spinal
roots. Teasing of the myelinated fibers was technically difficult, but theremnant fibers showed demyelination pattern (Fig. 1G-K). In somenerves, tomacula formation (focal myelin thickening) was observed(Fig. 1G-K arrowheads), which were compatible with the pathologicalreport of patients having periaxin mutations [2]. These nerves showed
no cellular infiltration or thickening of the perineurium in these nerves.
Generalized neuronal loss was not found in the anterior horn of thespinal cord, the dorsal root ganglion, sympathetic ganglion, or oculo­
motor nucleus. Grouped atrophy was observed in the diaphragm muscle
on HE stains [3].

https://doi.org/10.1016/j.ensci.2021.100358
Received 8 May 2021; Received in revised form 5 July 2021; Accepted 11 July 2021
Available online 13 July 2021
2405-6502/© 2021 The Authors.
Published by Elsevier B.V. This isanopenaccessarticle(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Please cite this article as: Kengo Maeda, eNeurologicalSci, https://doi.org/10.1016/j.ensci.2021.100358

undertheCC

BY-NC-ND

licenseK. Maeda et al.

eNeurologicalSci xxx (xxxx) xxx

Fig. 1. Toluidine blue staining of the anterior spinal nerve root (A), the posterior spinal nerve root (B), the recurrent laryngeal nerve (C), the vagal nerve (D), thephrenic nerve (E), and the oculomotor nerve (F). Bars in the bottom right corners represent 20 μm. Teased fibers of the anterior spinal nerve root (G), the posterior
spinal nerve root (H), the recurrent pharyngeal nerve (I), the vagal nerve (J), and the phrenic nerve (K). The bar in the bottom represents 100 μm. Tomacula
formation (focal myelin thickening) is observed in these nerves (arrowhead). (For interpretation of the references to colour in this figure legend, the reader is referredto the web version of this article.)

3. Discussion

Acknowledgement

The likely cause of her death included asphyxia by food aspiration or
acute respiratory failure by the bilateral recurrent laryngeal nerve palsy.
Although she had no dyspnea in daytime, there was evidence of aspi­
ration pneumonia. The strength of cough might have been insufficientdue to the latent demyelination of the phrenic nerve. Decreased
pharyngeal reflex might have been associated with her aspiration.
Periaxin is a protein expressed by Schwann cells. Homozygous mu­
tations of this gene cause demyelinating polyneuropathy. Nonsense orframeshift mutation of this gene results in early onset CMT4F or
Dejerine-Sottas neuropathy [2]. The pathological evidence of phrenic
nerve involvement in Dejerine-Sottas disease has been reported [4].
Electrophysiological report on the phrenic nerve has been also publishedin other type CMT [5]. Vocal cord paresis due to dysfunction of therecurrent laryngeal nerve has been reported in CMT2 with mitofusin-2mutation, CMT2C with transient receptor potential cation channel
subfamily V member 4 mutation, CMT4A with ganglioside-induced
differentiation-associated protein 1 mutation, and CMT4B1 withmyotubularin-related protein 2 mutation [6]. Although the recurrent
laryngeal nerves would undergo pathological change in CMT as well as
the nerves innervating limbs, there has been no pathological evidence of
this nerve to the best of our knowledge. Dysfunction of these nerves
causes hoarseness or dyspnea.
Oculomotor nerve palsy has been reported in a patient with CMT1A[7]. It is difficult to evaluate oculomotor nerves electrophysiologically,and pathological changes of oculomotor nerves in CMT is rarely re­ported. Demyelination of the oculomotor nerve in our patient wasobvious compared to those of patients without CMT [8].

The authors would like to thank Editage (www.editage.jp) for the
English language review.

4. Conclusion

Kengo Maedaa,*, Yutaka Yamamotoa, Masatsugu Ohuchib,
Takuto Sakashitac, Masanori Shioharad, Tomo Namurad,
Masayuki Shintakue, Eiji Matsuuraf, Hiroshi TakashimafaDepartment of Neurology, National Hospital Organization Higashi-ohmi
General Medical Centre, Higashi-ohmi, Shiga, Japanb
Department of General Thoracic Surgery, National Hospital Organization
Higashi-ohmi General Medical Centre, Higashi-ohmi, Shiga, Japanc
Department of Respiratory Medicine, National Hospital Organization
Higashi-ohmi General Medical Centre, Higashi-ohmi, Shiga, JapandDivision of Diagnostic Pathology, Shiga University of Medical ScienceHospital, Otsu, Shiga, Japane
Department of Pathology, Hikone Municipal Hospital, Hikone, Shiga,
Japan

References[1] S. Tokunaga, A. Hashiguchi, A. Yoshimura, K. Maeda, T. Suzuki, H. Haruki,
T. Nakamura, Y. Okamoto, H. Takashima, Late-onset Charcot-Marie-Tooth disease
4F caused by periaxin gene mutation, Neurogenetics 13 (2012) 359–365, https://doi.org/10.1007/s10048-012-0338-5.
[2] H. Takashima, C.F. Boerkoel, P. De Jonghe, C. Ceuterick, J.J. Martin, T. Voit, J.
M. Schröder, A. Williams, P.J. Brophy, V. Timmerman, J.R. Lupski, Periaxin muta­
tions cause a broad spectrum of demyelinating neuropathies, Ann. Neurol. 51 (2002)
709–715, https://doi.org/10.1002/ann.10213.
[3] M. Shintaku, K. Maeda, M. Shiohara, T. Namura, R. Kushima, Neuropathology of the
spinal nerve roots, spinal cord, and brain in the first autopsied case of CharcotMarie-Tooth disease 4F with a mutation (D651N) of the periaxin gene, Neuropa­
thology (2021), https://doi.org/10.1111/neup.12731 (in press).
[4] K.J. Felice, J.D. Fratkin, E.L. Feldman, A.A. Sima, Phrenic nerve involvement in
Dejerine-Sottas disease: a clinicopathological case study, Pediatr. Pathol. 14 (1994)
905–911.
[5] L. Sagliocco, G. Orlandi, R. Calabrese, A. Pellengrinetti, O. Baglini, F. Castelli,
F. Baldinotti, F. Sartucci, Electrodiagnostic evidence of phrenic nerve demyelinationin Charcot-Marie-Tooth disease 1A, Am. J. Phys. Med. Rehabil. 82 (2003) 754–759,
https://doi.org/10.1097/01.PHM.0000087453.94529.0D.
[6] A.A. Zambon, M.G.N. Sora, G. Cantarella, F. Cerri, A. Quattrini, G. Comi, S.
C. Previtali, A. Bolino, Vocal cord paralysis in Charcot-Marie-Tooth type 4b1 diseaseassociated with a novel mutation in the myotubularin-related protein 2 gene: a casereport and review of the literature, Neuromuscul. Disord. 27 (2017) 487–491,
https://doi.org/10.1016/j.nmd.2017.01.006.
[7] A. Posa, A. Emmer, M.E. Kornhuber, Unilateral oculomotor palsy in Charcot-MarieTooth disease 1A (CMT1A), Clin. Neurol. Neurosurg. 155 (2017) 20–21, https://doi.
org/10.1016/j.clineuro.2017.02.004.
[8] K. Maeda, H. Yasuda, Histological background of susceptibility of oculomotor nerve
to ischemia, J. Neurol. Disord. Stroke 3 (2014) 1092.

In conclusion, we must pay attention to respiratory function andcranial nerve palsies in hereditary demyelinating neuropathies.
Grant support
This report received no specific grant from any funding agency inpublic, commercial, or not-for-profit sector.
Declaration of Competing InterestNone.
2K. Maeda et al.
feNeurologicalSci xxx (xxxx) xxx*Department of Neurology and Geriatrics, Kagoshima University Graduate
School of Medical and Dental Sciences, Kagoshima, Japan

3Corresponding author at: Department of Neurology, Vories Memorial
Hospital, 492 Kitanosho, Omi-hachiman, Shiga 523-8523, Japan.
E-mail address: maeda@vories.or.jp (K. Maeda).