Hirayama Disease: Case Report / Doença de Hirayama: Relato de caso

Abstract A 26-year-old previously healthy patient who, at the age of 18 years, began progressive loss of distal strength, rest tremor, and muscle atrophy in the left upper limb. Upon examination, the patient presented moderate distal atrophy, degree 4 in muscular strength, and minipolymioclonus. Electromyoneurography revealed (EMNG) chronic preganglionic bilateral involvement of bilateral C7/C8/T1, worse on the left, with signs of active C8/T1 denervation. A cervical spine magnetic resonance imaging (MRI) scan showed spondylodiscal degenerative changes with central protrusions in C4-C5, C6-C7, and right central in C5-C6, which touched the dural sac. The anteroposterior diameter of the medulla in neutral position, in the C5-C6 plane, was of 5.1 mm. There was a reduction of the spinal cord caliber to 4.0 mm after the dynamic maneuver of forced flexion of the spine, as well as signal increase in the anterior horns. The clinical findings and those of the complementary tests were compatible with Hirayama disease (HD), a rare benign motor neuron disease that affects cervical spinal segments and is most prevalent in men, with onset in the early 20s. Unilateral and slowly progressive weakness is typical, but self-limited. Sensory disturbances, and autonomic and upper motor neuron signals are rare. Management is usually conservative, with the use of a soft cervical collar. Although rare, HD should be considered in young patients with focal asymmetric atrophy in the upper limbs. The early diagnosis of HD depends on the degree of suspicion, as well as on the cooperation and communication among the various specialties involved in the investigation.

Resumo Paciente de 26 anos, previamente hígido, que, aos 18 anos, iniciou perda progressiva de força distal, tremor de repouso, e atrofia muscular no membro superior esquerdo. Ao exame, apresentou atrofia moderada, distal, força muscular de grau 4, e minipolimioclonus. A eletroneuromiografia (ENMG) revelou comprometimento pré-ganglionar crônico de C7/C8/T1 bilateral pior à esquerda, com sinais de desnervação ativa em C8/T1. A ressonância magnética (RM) de coluna cervical mostrou alterações degenerativas espondilodiscais com protrusões centrais em C4-C5, C6-C7, e central direita em C5-C6, que tocavam o saco dural. O diâmetro anteroposterior da medula na posição neutra, no plano de C5-C6, era de 5,1 mm. Houve redução do calibre da medula para 4,0 mm após a manobra dinâmica de flexão forçada da coluna, e aumento de sinal nos cornos anteriores. Os achados clínicos e os dos exames complementares eram compatíveis com doença de Hirayama (DH), uma doença benigna rara dos neurônios motores, que afeta os segmentos espinhais cervicais e é mais prevalente em homens e de início próximo aos 20 anos. É típica a fraqueza unilateral e lentamente progressiva, porém autolimitada. Perturbações sensoriais, sinais autonômicos e do neurônio motor superior são raras. O manejo geralmente é conservador, com uso de colar cervical macio. Apesar de rara, a DH deve ser considerada em pacientes jovens que apresentam atrofias assimétricas focais de membros superiores. O diagnóstico precoce de DH depende do grau de suspeição, e da cooperação e comunicação entre as diversas especialidades envolvidas na investigação.

Bilateral Hirayama Disease: A Case Report

Hirayama disease is a rare restricted form of motor neuron disease. It commonly affects young males. Patients typically presentwith the insidious onset of unilateral weakness and atrophy of the hand muscles that often progresses to the forearm. In somecases, the syndrome is bilateral but often asymmetrical. Of note, the brachioradialis muscle is usually spared. The syndromeaffects C7–C8–T1 muscles with sparing of the C5–6 muscles. We report a case of a 25-year-old male who presented with 2years of history of progressive wasting and weakness of muscles of bilateral hands and forearms. Based on clinical features,electrodiagnostic studies and dynamic magnetic resonance imaging cervical spine diagnosis of Hirayama disease were made.The patient was treated conservatively with a cervical collar. Over a period of 8 months follow-up, no progression was seen.

Two Cases of Hirayama Disease in a Pediatric Clinic / 대한소아신경학회지

We report two pediatric cases with Hirayama disease—a 16-year-old boy with a left wrist drop and a 14-year-old-boy with weakness and muscle atrophy of right hand. Motor nerve conduction study revealed decreased motor nerve action potential amplitudes in the ulnar nerve and radial nerve of the affected hands. The former patient showed normal magnetic resonance imaging (MRI) of the cervical spine, but the latter showed mild, asymmetric thinning of the anterior spinal cord at levels C5 to C7. Following active rehabilitation and avoidance of neck flexion, no further progression of neurological findings was noticed. These clinical findings were typical of Hirayama disease. We show that timely and accurate diagnosis for Hirayama disease is possible with awareness of disease history, careful physical examination, and the use of neurophysiological studies and MRI studies.

Resonancia magnética de columna cervical con secuencia en flexión para el diagnóstico de la enfermedad de Hirayama / Magnetic resonance of the cervical spine with sequence in flexion for the diagnosis of Hirayama disease

La enfermedad de Hirayama o atrofia muscular espinal juvenil no progresiva de las extremidades superiores es una clase de mielopatía relacionada con la flexión del cuello. Afecta principalmente a hombres jóvenes (entre 15 y 25 años) y se caracteriza por una debilidad muscular asimétrica y unilateral de miembros superiores con atrofia. Suele presentarse de manera insidiosa, con curso progresivo y autolimitado a los 3-4 años del inicio del cuadro. Se cree que es producida por trastornos isquémicos en la microcirculación de las astas anteriores del segmento medular cervical entre C8 y T1 por la compresión en el segmento medular anterior debido al desplazamiento anterior de la duramadre al flexionar el cuello. Si bien existen varias teorías sobre la causa de este deslizamiento, la más aceptada se relaciona con la falta de crecimiento de la duramadre con respecto a la columna durante la pubertad. Esto provocaría un aumento de la tensión de la dura posteriory, como consecuencia, el desplazamiento anterior durante la flexión. Dado su excelente contraste tisular y la posibilidad de realizar adquisiciones en distintos planos, la resonancia magnética es el estudio de elección. Las imágenes deben ser obtenidas en posición neutra y en flexión cervical máxima para poner de manifiesto el desplazamiento de la dura, con el consiguiente aumento de la sensibilidad y especificidad de la prueba. Así, se logra mayor confianza en el diagnóstico y menor cantidad de falsos positivos, en comparación con la posición neutra como única adquisición.

Hirayama disease is a type of myelopathy related to neck flexion. It affects young male adults between 15 and 25 years, and is characterised by unilateral and asymmetric upper limb muscle weakness with atrophy. It usually presents insidiously, with a progressive course and self-limits in 3-4 years. It is believed that it could be produced by ischaemic disorders in the microcirculation of the anterior horns of the cervical spine segment C8 and T1 due to anterior displacement of the dura. There are several theories for the cause of this displacement, with the most accepted being the relationship between the lack of growth of the dura mater and the spine during puberty. This increases the tension of the posterior dura mater and consequently the anterior displacement during flexion. Due to its excellent tissue contrast and the possibility of acquisitions in different planes, magnetic resonance imaging is the study of choice. Images must be obtained in both neutral and cervical flexion to highlight the displacement of the dura mater. This increases the sensitivity and specificity of the test, giving greater confidence in the diagnosis, and reducing false positives compared to neutral as a single acquisition.

The imageological advances in Hirayama disease / 复旦学报（医学版）

Hirayama disease is benign and self-limited,characterized by atrophy of unilateral upper extremity.Misdiagnosis was common due to the restriction of diagnostic techniques in the past.In recent years,Hirayama disease is familiar to us because of the rapid development of electromyography and imageological examinations.X-ray and CT scan play an important role in evaluations on cervical curvature,segmental stability,degeneration of facet joints and posterior longitudinal ligament.Loss of attachment in neutral cervical MRI and anterior shift of dura mater in flexion cervical MRI are the most important signs.This review summarizes the imageological examinations and characteristic signs of Hirayama disease in detail,together with a brief introduction to clinical manifestations and electromyography features.

Midterm clinical outcomes and radiological results of surgical treatment for Hirayama disease / 北京大学学报(医学版)

Objective:To assess the midterm clinical and radiological outcomes of internal fixation and fusion for the treatment of Hirayama disease and to evaluate the clinical significance and value of this procedure.Methods:In the study,36 patients were treated with anterior cervical internal fixation and fusion.The clinical outcomes including muscle strength and atrophy were recorded.The radiological outcomes including range of motion of cervical spine and the cross-sectional area of spinal cord at each level on MRI scan were measured before and at 3 month,1 year and 2 years follow-up time points after surgery.Results:(1) Clinical outcomes:all the patients showed no further progression of symptoms except one patient with mild progression of muscular weakness and atrophy.As the time passed by,the ratio of the patients with muscle strength and atrophy improvement increased.There were 26.5 ％ of patients in 3 months,36.0％ in 1 year and 85.7％ in 2 years who experienced muscle strength improvement.8.8％ of patients in 3 months,24.0％ in 1 year and 35.8％ in 2 years felt muscle atrophy improvement.And 12 of the 14 patients showed improved muscle strength and atrophy at the end of 2 years period follow-up.(2) Radiological outcomes:the range of motion (ROM) of C2-C7 was significantly decreased after the operation.The ROM of preoperation was 62.25° ±2.10° and that of 2 years postoperation was 13.67° ± 7.51°(P ＜ 0.01).The spinal cord was of no compression on flexion MRI.The cross-section area of spinal cord on MRI was significantly increased only at C6 level (P ＜0.05) at the end of three months follow-up.The level of increased cross-section area rose to C4-C5-C6 levels (P ＜0.01) in 1 year and to C4-C5-C6-C7 levels at the end of 2 years follow-up P ＜ 0.05).The cross-section area increased 15.60％ at C4,19.08％ at C5,21.60％ at C6 and 23.91％ at C7 with significant difference (P ＜0.05) 2 years after the operation.Conclusion:Anterior cervical internal fixation and fusion is an effective surgical treatment for Hirayama disease and may provide preferable midterm clinical and radiological outcomes.This procedure has clinical significance and value in terms of control of the progression and outcome of this disease.

Hirayama Disease with Proximal Involvement

Hirayama disease is a slowly progressing benign motor neuron disease that affects the distal upper limb. A 29-year-old man visited the hospital with a 1-year history of weakened left proximal upper limb. He was diagnosed with Hirayama disease 9 years ago, while there was no further progression of the muscle weakness afterward. Atrophy and weakness was detected in proximal upper limb muscles. Magnetic resonance imaging and somatosensory evoked potentials were normal. Needle electromyography showed abnormal findings in proximal upper limb muscles. Our patient had Hirayama disease involving the proximal portion through secondary progression. Clinical manifestation and accurate electromyography may be useful for diagnosis. Rare cases with progression patterns as described here are helpful and have clinical meaning for clinicians.

Clinical Experiences of Uncommon Motor Neuron Disease: Hirayama Disease

Hirayama disease, juvenile muscular atrophy of the distal upper limb, is a rare disease predominantly affecting the anterior horn cells of the cervical spinal cord in young men. This cervical myelopathy is associated with neck flexion. It should be suspected in young male patients with a chronic history of weakness and atrophy involving the upper extremities followed by clinical stability in few years. Herein, we report 2 cases of Hirayama disease on emphasis of diagnostic approach and describe the pathognomonic findings at flexion magnetic resonance imaging.

Value of natural position of cervical vertebra using MRI in diagnosis of Hirayama disease / 实用放射学杂志

Objective To analyze the MRI features of Hirayama disease(HD)with cervical natural position and its diagnostic val-ue.Methods The natural position of cervical vertebra with MRI examination was used in 1 5 patients and 40 normal people.The spe-cificity and sensitivity of MRI features were analyzed and the ratio of cervical sagittal diameter/cervical transverse diameter (CSD/CTD)of the lower cervical cord was measured.Results CSD/CTD of the patients and control group had a significant difference (t=7.99,P =0.00).The sensitivity of LOA was 86.7%,and its specificity was 88.4%.The sensitivity of atrophy of the lower cervical cord was 80.0%,and its specificity was 79.5%.The sensitivity of the cervical spine curvature abnormalities was 40.0%,and its spe-cificity was 65.2%.The sensitivity of abnormal signal in the spinal cord was 46.7%,and its specificity was 87.5%.The sensitivity of abnormal signal in the epidural outer cavity was 20.0%,and its specificity was 96.8%.Conclusion MRI features of lower cervical cord in combination with clinical symptoms and signs can be helpful for the accurate diagnosis of HD.

Enfermedad de hirayama en un adolescente / Hirayama disease observed in an adolescent

La Enfermedad de Hirayama -o amiotrofia monomélica- es una afección de baja frecuencia y escasamente reportada en la edad pediátrica. Se presenta el caso clínico de un adolescente de 15 años de edad con disminución de la fuerza muscular y pérdida de la masa muscular, que comenzó a los 10 años de edad por la mano izquierda, y le afectó posteriormente el antebrazo. Mantuvo un curso progresivo durante 3 años, para luego mantenerse estable. El electromiograma de aguja arrojó lesión de axones motores o motoneuronas dependientes de los miotomas C7-T1, y en menor grado, C5-C6. En la tomografía axial computarizada con contraste endovenoso en marcada flexión cervical, se observó desde C7-T2 una evidente ectasia venosa posmedular asimétrica, predominantemente del lado izquierdo, por congestión del plexo venoso vertebral posterior interno. En este paciente la enfermedad se detuvo espontáneamente, en otros casos es necesario limitar la motilidad de la columna con el uso de un collar cervical, y solo llegar a la cirugía en los casos más severos de evolución rápida.

Hirayama disease or monomelic amyotrophy is a low frequent, barely reported illness at pediatric ages. Here is the clinical case of 15 years-old boy that presented with reduced muscular strength and loss of muscle mass; this condition began at the age of 10 year in his left hand and then affected the forearm. The illness progressed for three years and then remained stable. The needle electromyogram showed a lesion in C7-T1 myotome-depending motor axons or motoneurons and to less extent in those C5-C6 depending ones. The venous contrast computed tomography on a marked cervical cord flexion position; it was observed an evident asymmetric postmedullary vein ectasia from the C7-T2 myotomes, mainly on the left side, caused by the internal posterior vertebral vein plexus congestion. There was spontaneous remission of the disease in this patient, but it is necessary in other cases to limit the cervical cord motility with the use of a collar and to only perform surgery in the most rapidly evolving and severe cases.

Monomelic Amyotrophy after Permethrin Poisoning.

Monomelic amyotrophy (MMA) known as Hirayama disease (HD). The first report appeared in 1959 when Hirayama described 12 patients [1] then, a large group of patients was found from Japan [2,3]. MMA from South India was also reported in 1984 [4]. The disease accounted for males over 80% of cases, especially between 15 and 25 years of age. The disorder has been recognized as, unilateral or bilateral asymmetric atrophy of hand and forearm with sparing of brachioradialis giving the characteristic appearance of oblique amyotrophy. Symmetrically bilateral disease has also been recognized. It is believed to be a cervical flexion myelopathy [5]. Pyrethroids are used as insecticides due to their high potency. These are highly toxic to a wide range of insects but have low toxicity to humans. Pyrethroids are known to cause neurotoxicity in humans like seizures, tremors, and dizziness. Motor neuron damage has been reported in acute toxicity due to ingestion of pyrethroids and organochlorines [6] and MND (Motor neuron disease) like features after chronic exposure has been reported [7]. Here a case of monomelic amyotrophy following massive ingestion of permethrin, amytriptyline and benzodiazepine tablets is reported.

The Abnormalities in Neuro-Imaging and Somatosensory Evoked Potentials in Hirayama Disease / 대한임상신경생리학회지

No abstract available.

Severe Spinal Injury in Hirayama Disease

Hirayama disease is a rare neurological disorder characterized by an insidious progressive subacute unilateral or bilateral weakness of the hands and forearm muscles leading to a painless amyotrophy. The disease primarily affects young men in the second to third decades of life. It has always been described as a second motor neuron disease, thus sparing the pyramidal and sensitive pathways. It usually has a slow progression course of 3 to 5 years followed by stabilization. Since its initial description by Keyzo Hirayama in 1959, most cases have been reported in Asia, particularly Japan and India, although the disease reportedly has worldwide distribution.

To evaluate the cervical spine curvature and growth rate for studying the pathogenesis of Hirayama disease in adolescents / 中华内科杂志

Objective To explore the pathogenesis of Hirayama disease from juvenile cervical curvature and growth rate.Methods Totally 60 patients diagnosed with Hirayama disease (HD) from 2009 to 2011 in our hospital were included in the present study.Patient's height and growth rate 1-2 years prior to the onset of disease were recalled by patients and family members.Lateral cervical X-ray was examined,and cervical curvature was measured by Borden's method.Results All the patients were adolescents with onset age at 12-25 (17.0 ± 2.4) years old and peak age of onset at 15-18 [45 cases (75.0％)].Fifty-seven cases were male and 3 cases were female.Cervical MRI examination of the 60 cases showed that the spinal cord atrophy involving C4-C8 vertebral level.The C line values for cervical curvature by Borden's method of the patients was 2.6 (1.2,4.2) mm.Among 60 patients,57 of them were with abnormal cervical curvature.The average height growth rate 1 year prior to the onset was (7.1 ± 1.8) cm.Conclusions The clinical manifestations that featured in overgrowth in the first two years and abnormal cervical vertebra curvature are possible related with pathogenesis of HD.HD is possibly a cervical spinal cord compression disease,which is associated with cervical spinal dysplasia during juvenile growth.

Response of Hirayama disease to surgical intervention: case report.

Hirayama disease also known as monomelic amyotrophy, primarily involves distal upper limb extremities. It differs from the known types of motor neuron diseases because of its nonprogressive behavior and pathologic findings of focal ischemic changes in the anterior horn of the lower cervical cord. We present a young male with Hirayama disease who had a left upper extremity involvement which was progressive in nature. He didn’t respond with initial treatment of cervical collar. Consequently surgical intervention improves muscle weakness and decrease the neurological deficit.

The CT morphological difference of luscka joint between Hirayama disease patients and non-Hirayama disease patients / 中国脊柱脊髓杂志

Objectives: To study the morphological difference of luscka joints between Hirayama disease patients and non-Hirayama disease patients on CT scan and to provide a new possible mechanism of Hirayama disease. Methods: 32 patients(all males) with a mean age of 19.4±4.1(range 16-37 years) and with Hirayama disease were treated in our hospital from October 2006 to January 2012, the mean course of disease was 31.7±23.7 months(range, 1-120 months). 32 patients(all males) with a mean of age was 19.1±4.3 (range, 12-26 years) suffering from acute neck pain and having no Hirayama disease were reviewed as control. Both groups showed no age related difference. From the cervical CT coronal plane reconstruction images which passing through the transverse foramen center of C3-C7 in GE-PACS system, the following data were measured in both sides: ①The width of the uncinate process base: the distance between inner and outer margin of the uncinate process at the upper edge of the vertebral body. ②The height of the uncinate process:the vertical distance from the top of the uncinate process to the upper edge of the vertebral body. ③The distance between two uncinate processes: the distance between the tips of the bilateral uncinate processes. ④The inclination angle of the uncinate process: the angle between the uncinate process and the upper edge of the vertebral body. ⑤The inclination angle of the inferior endplate: the angle between the uncinate process:the vertical distance from the top of the uncinate process to the upper edge of the vertebral body. Results:There were no significant side-related differences on the width of the uncinate process base, the height of the uncinate process, the distance of the uncinate process, the inclination angle of the uncinate process and the inclination angle of the inferior endplate at the same segment from C3 to C7 in Hirayama disease patients(P>0.05). However, differences were found on the height of the uncinate process and the distance between two uncinate processes of C3-C7 (PC5>C7>C3>C4. The distance of the uncinate process gradually increased from C3 to C7. There were no significant differences on the width of the uncinate process base, the inclination angle of the uncinate pro-cess and the inclination angle of inferior endplate(except for C3) of C3-C7(P>0.05). Then, using the mean value of the left and right sides as the width of the base of uncinate process, the height of uncinate process, and calculating the sum of inclination angle of the uncinate process, the sum of inclination angle of inferior endplate of the upper vertebra and the difference between the sums (the sum of inclination angle of uncinate process - the sum of inclination angle of inferior endplate of the upper vertebra), then calculating the mean value and standard deviation. Compared with the non-Hirayama disease patients, there were no significant dif-ferences on the uncinate process base, the distance of the uncinate process and the sum of inclination angle of the uncinate process at the same segment of Hirayama disease patients (P>0.05), while the height of the uncinate process and the sum of inclination angle of uncinate process of Hirayama disease patients were sig-nificantly smaller than those of the control group, respectively(P<0.05), and the differences between the sums were larger than those of the control group (P<0.05). Conclusions: Hirayama disease patients may possess a dysplasia in the luscka joint, manifesting the nonuniform development of the uncinate indicators. Lower unci-nate process and smaller inclination angle of inferior endplate of the upper vertebra are common, The conse-quential cervical instability may play a significantly important role in the pathogenesis and progress of Hi-rayama disease.

The correlation of clinical appearance and the variation of disc-facet angle in Hirayama disease / 中国脊柱脊髓杂志

Objectives: To reveal the possible role and mechanism of disc-facet angle in the occurrence and progress of Hirayama disease by analyzing the correlation of clinical appearance and the variation of disc-facet angle in Hirayama disease. Methods: 45 patients with Hirayama disease treated in the orthopedic de-partment of Peking University Third Hospital from October 2006 to January 2012 were reviewed. There were 44 males(97.8%) and 1 female(2.2%) with an average age of 19.33±3.89(range 13-37) years old. The onset age was 16.33±2.73 (range 10-27) years old and the duration of history was 35.64±23.24 (range 1 to 120) months. The disc-facet angle of C3-T1 was measured on PACS system. An extension line was made along the upper edge of objective vertebral body on the CT scan sagittal reconstruction image. An extension line was made along the joint surface of upper articular process of objective vertebra on the sagittal plane which crossed the midpoint of the facets. The blunt angle between two lines was the disc-facet angle. The cases were divided into unilateral affect and bilateral affected group according to history, spinal cord function and spinal cord lesion level. The correlation of above data and the variation of disc-facet angle were analyzed. Results: The duration of history in unilateral affected patients was significantly shorter than that of bilateral affected patients (P<0.05). The duration of history in sequential onset patients was significantly shorter than that of simultaneous onset in bilateral affected patients (P<0.05). The JOA score 17 and Chinese score 40 in unilateral affected patients were higher than those of bilateral affected patients. The C3-C7 disc-facet angle of affected side was bigger than that of normal side in unilateral affected patients, and C5, C6 had statistically significant difference (P<0.05). The spinal cord lesion level was mainly at C5 and C6 in unilateral affected group. The disc-facet angle had no difference on both sides in bilateral affected patients but the figures at C4 and C5 level were bigger than that of normal side in unilateral affected patients. The spinal cord lesion level was mainly at C4 and C5 in bilateral affected group. The stability of upper cervical spine segments was even worse in unilateral affected group and resulting in higher level of spinal cord lesion comparing with bi-lateral affected group. Conclusions: The disc-facet angle of C4, C5 is bigger in bilateral affected patients and may be correlated with higher level spinal cord lesion and more severe clinical symptoms. The C5, C6 disc-facet angle of affected side is significantly bigger than that of normal side in unilateral affected patients. This may be the key factor of spinal cord lesion mainly at C5 and C6 level on the same side.

A Case of the Hirayama Disease in Young Male Adolescent / 대한소아신경학회지

In the present study, we report muscular atrophy of the right distal upper extremity in a 14-year-old boy. The disease progressed insidiously for about 2 years, and during our first examination, he exhibited weakness and wasting in the right hand, and paresthesia on the C6-8 dermatomal area in the right upper extremity. Electromyography revealed neurogenic changes in atrophic muscles. Conduction velocity of the ulnar nerve of the affected hand was decreased. Magnetic resonance imaging (MRI) of the cervical spine in the neutral position revealed focal spinal cord atrophy and a small area of high signal intensity at C5-6 level. In the flexion-induced cervical spine MRI scan, the spinal cord was noticed to be compressed by the posterior dural sac with a forward shift and flow voids in the epidural space. All these parameters led to the diagnosis of Hirayama disease (HD). This is the first report of HD in Korea by pediatrician, even though it is characterized by juvenile onset.

An electrophysiological study of Hirayama disease / 中华物理医学与康复杂志

Objective To analyze the electrophysiological characteristics of Hirayama disease and explore their significance for its diagnosis.MethodsElectrophysiological tests were performed on 18 patients who fulfilled the clinical criteria for Hirayama disease. Sixteen were males and 2 were females. The mean age was 24.9years old ( 19-58 years), and the mean case history was 5.2 years ( 1-40 years). The Hirayama disease was clearly unilateral in 10 patients and bilateral in 3, with 5 cases suspected of being bilateral. Motor neuron conduction velocity (MCV) and sensory neuron conduction velocity (SCV) were measured in the median and ulnar nerves.Electromyograms (EMGs) of the abductor digiti minimi, abductor pollicis brevis, extensor digitorum communis,brachioradialis muscle, biceps brachii and sternocleidomastoid were recorded in all cases. The MCV and SCV of the common peroneal nerve and an EMG of the tibialis anterior muscle were examined in one leg. The MCV and SCV of the ulnar nerve and EMGs of the abductor digiti minimi, extensor digitorum communis and brachioradialis muscles were inspected on the contralateral sides of 8 cases, including the patients suspected of suffering bilateral Hirayama disease. The MCVs of the median and ulnar nerves were examined segmentally by stimulating the nerves distally as well as proximally, and recording the amplitude, duration and area of compound muscle action potentials (CMAP) and changes in wave form, then determining whether there was a nerve conduction block.Results (1) No conduction block was detected in any median nerve or ulnar nerve among the 18 cases. (2) All the SCVs and sensory nerve action potentials of the median and ulnar nerves were normal. ( 3 ) All the MCVs and SCVs of the common peroneal nerve and the EMGs of the anterior tibialis muscles were normal. (4) MCV slowing in the upper limbs accounted for 41.3％ (19/44) of the examined nerves. The rates of MCV decrease were 72.2％ (13/18)in the ulnar nerve on the affected sides, 33.3％ (6/18) in the median nerve on the affected sides and 0％ (0/8)in the ulnar nerve on the contralateral sides. (5) Amplitude reduction in the CMAP in the upper limbs accounted for 81.8％ (36/44) of the examined nerves. The rates of amplitude decrease were 100％ (18/18) in the ulnar nerves of the affected sides, 77.8％(14/18) of median nerves on the affected side and 50％(4/8) of ulnar nerves on the contralateral side. ( 6 ) Upper limb EMGs revealed a rate of neurogenic damage of 47.0％ ( 62/132). The EMGs decreased in 100％ (18/18) of the abductor digiti minimi and abductor pollicis brevis on the affected side, 88.9％ (16/18) of extensor digitorum communis on the affected side, 62.5％ (5/8) of the abductor digiti minimi on the contralateral side, 37.5％ (3/8) of the extensor digitorum communis on the contralateral side,5.6％ ( 1/18 ) of the brachioradialis and biceps brachii muscles on the affected sides. There was no neurogenic damage of the contralateral brachioradialis muscle or the sternocleidomastoid on the affected side.Conclusions The electrophysiological features of Hirayama disease include unilateral or bilateral neurogenic damage in the upper limbs. According to the abnormal EMGs, spinal anterior horn cells on the affected sides were injured at C7-T1. C6and above C6 were rarely involved. The electrophysiological characteristics of Hirayama disease could provide a clear basis for localization and differentiation in Hirayama disease diagnosis.

Clinical Characteristics, Electrodiagnostic, and Imaging Findings of Atypical Forms of Motor Neuron Disease

OBJECTIVE: To describe the clinical characteristics, electrodiagnostic, and imaging findings of Hirayama disease (HD), late onset monomelic amyotrophy (LMA), and brachial amyotrophic diplegia (BAD). METHOD: A retrospective analysis of the medical records, electrodiagnostic, and imaging findings of 12 patients (4 HD, 2 LMA, 6 BAD) was done. For patients whose last clinic follow-up exceeded 6 months a telephone survey was done to see if there were any symptom changes. RESULTS: The clinical, electrodiagnostic, and imaging findings of the HD and BAD patients were similar to previous studies. Except for a later onset, age disease duration was too short to distinguish LMA from HD or other motor neuron diseases. One patient in the BAD group progressed to amyotrophic lateral sclerosis (ALS) and another died due to undetermined respiratory failure. These two patients showed abnormalities in their lower extremities, thoracic paraspinal, and craniocervical muscles on needle electromyography. Except for another patient, none of the other three patients showed abnormalities in their lower extremities, thoracic paraspinals, or craniocervical muscles on needle electromyography. CONCLUSION: HD and BAD can be considered as separate disease entities. However, a longer follow-up period than previously recommended is necessary to differentiate BAD from ALS. Follow-up period was too short to determine whether LMA can also be considered as a separate disease entity.