Amyotrophic Lateral Sclerosis Mimic Syndrome in a 24-Year-Old Man with Chiari 1 Malformation and Syringomyelia: A Clinical Case

Chiari 1 Malformation (CM1) is classically defined as a caudal displacement of the cerebellar tonsils through the foramen magnum into the spinal cord. Modern imaging techniques and experimental studies disclose a different etiology for the development of CM1, but the main etiology factor is a structural defect in the skull as a deformity or partial reduction, which push down the lower part of the brain and cause the cerebellum to compress into the spinal canal. CM1 is classified as a rare disease. CM1 can present with a wide variety of symptoms, also non-specific, with consequent controversies on diagnosis and surgical decision-making, particularly in asymptomatic or minimally symptomatic. Other disorders, such as syringomyelia (Syr), hydrocephalus, and craniocervical instability can be associated at the time of the diagnosis or appear secondarily. Therefore, CM1-related Syr is defined as a single or multiple fluid-filled cavities within the spinal cord and/or the bulb. A rare CM1-related disorder is syndrome of lateral amyotrophic sclerosis (ALS mimic syndrome). We present a unique clinical case of ALS mimic syndrome in a young man with CM1 and a huge singular syringomyelic cyst with a length from segment C2 to Th12. At the same time, the clinical picture showed upper hypotonic-atrophic paraparesis in the absence of motor disorders in the lower extremities. Interestingly, this patient did not have a disorder of superficial and deep types of sensitivity. This made it difficult to diagnose CM1. For a long time, the patient’s symptoms were regarded as a manifestation of ALS, as an independent neurological disease, and not as a related disorder of CM1. Surgical treatment for CM1 was not effective, but it allowed to stabilize the course of CM1-related ALS mimic syndrome over the next two years.


Introduction
Chiari malformation type 1 (CM1) is characterized by the caudal descent of the cerebellar tonsils through the foramen magnum at least 5 mm in adults, measured using the McRae line drawn from the basion to the opisthion [1][2][3]. Nearly 33% of patients with

Patient History
A Caucasian male, 23 years old, married with 2 children. He is a bus driver. This patient has been under our observation for 4 years. He complained on a slight weakness, muscle wasting of both hands, loss of dexterity, and clumsiness with fine motor skills. The patient has no family history of CM1, Syr, and ALS. The age of onset was 19 years, when the patient first noticed a slight weakness when squeezing the right hand. Weakness in his arms gradually progressed. After 2 years, the patient showed progressive loss of muscle mass (hypotrophy) of the thenar, hypothenar and dorsal interosseous muscles of the right hand. However, these symptoms did not particularly prevent him from driving the bus. CM1-related Syr was first diagnosed at the age of 19 years after cervical spine MRI examination was ordered by a neurologist to exclude herniated disc and radiculopathy. At the age of 20 years, Syr-associated ALS mimic syndrome was first diagnosed based on neurological symptoms, as well as electromyography (EMG) and MRI findings. At the age of 22 years, the patient underwent suboccipital craniotomy with C1 laminectomy. After this operation, there was no significant increase in muscle weakness and atrophy of the muscles of the hands during the last year. Despite the progression of the disease, the patient is socially and professionally adapted to the present time.

Physical Examination
Consciousness is clear. The patient is oriented in his own personality, place, time, and space. Emotional lability is manifested by the inability to control the expression of emotions, but there are no cognitive impairments. Cranial nerves are normal.
A slight flexion deformity of the fingers of the hands (predominant on the right hand) was detected ( Figure 1). There is moderate hypotrophy of the muscles of both hands; it is more pronounced on the right. There are spontaneous periodic fasciculations of the muscles of the thenar and hypothenar of both hands (more on the left), intensified after a hammer percussion of muscle. Less pronounced spontaneous and induced fasciculations of the muscles of the shoulders and forearms were detected on both sides (more on the right).
J. Clin. Med. 2023, 12, x FOR PEER REVIEW 3 of 21 neuron (UMN). This form of ALS mimic syndrome may be associated with a reduced resistance of spinal motoneurons to hypoxia and compression compared to fibers of the pyramidal tracts in the lateral and anterior cortical-spinal tracts. However, Syr-associated ALS mimic syndrome is extremely rare in real clinical practice, which was the reason to present our evidence-based clinical case study of this disorder in a young Caucasian male.

Patient History
A Caucasian male, 23 years old, married with 2 children. He is a bus driver. This patient has been under our observation for 4 years. He complained on a slight weakness, muscle wasting of both hands, loss of dexterity, and clumsiness with fine motor skills. The patient has no family history of CM1, Syr, and ALS. The age of onset was 19 years, when the patient first noticed a slight weakness when squeezing the right hand. Weakness in his arms gradually progressed. After 2 years, the patient showed progressive loss of muscle mass (hypotrophy) of the thenar, hypothenar and dorsal interosseous muscles of the right hand. However, these symptoms did not particularly prevent him from driving the bus. CM1-related Syr was first diagnosed at the age of 19 years after cervical spine MRI examination was ordered by a neurologist to exclude herniated disc and radiculopathy. At the age of 20 years, Syr-associated ALS mimic syndrome was first diagnosed based on neurological symptoms, as well as electromyography (EMG) and MRI findings. At the age of 22 years, the patient underwent suboccipital craniotomy with C1 laminectomy. After this operation, there was no significant increase in muscle weakness and atrophy of the muscles of the hands during the last year. Despite the progression of the disease, the patient is socially and professionally adapted to the present time.

Physical Examination
Consciousness is clear. The patient is oriented in his own personality, place, time, and space. Emotional lability is manifested by the inability to control the expression of emotions, but there are no cognitive impairments. Cranial nerves are normal.
A slight flexion deformity of the fingers of the hands (predominant on the right hand) was detected ( Figure 1). There is moderate hypotrophy of the muscles of both hands; it is more pronounced on the right. There are spontaneous periodic fasciculations of the muscles of the thenar and hypothenar of both hands (more on the left), intensified after a hammer percussion of muscle. Less pronounced spontaneous and induced fasciculations of the muscles of the shoulders and forearms were detected on both sides (more on the right).  Thumb opposition strength decreased up to 2/5 points on the right hand and up to 4/5 points on the left hand. Metacarpophalangeal abduction strength of the fingers reduced up to 3/5 points on the right hand and up to 4/5 points on the left hand. Flexion strength of the second, third, fourth, and fifth fingers decreased up to 2/5 points on the right hand and up to 4/5 points on the left hand. Flexion and extension of the wrist slightly reduced on the right hand up to 4/5 points. The strength of the muscles of the forearms, shoulders, upper arm, neck, trunk, and lower extremities were normal (5/5 points).
The pathological reflexes Babinski, Chaddock, Oppenheim, Gordon, and Schaefer were absent. No coordination disorders were identified. Touch, vibration, temperature, position, and pain sensations were normal. There are no violations of defecation, urination, and erectile function.

Laboratory Results
Routine biochemical and hematologic study results were normal, including serum levels of 25OH(D 3 ), cyanocobalamin, thyroid hormones (T3, T4, thyroid-stimulating hormone), glycated hemoglobin, and creatine kinase. The serologic testing results for hepatitis B and C, human immunodeficiency virus, and Treponema pallidum were unremarkable.

Neuroimaging
Brain MRI: T1-and T2-weighted MRI scans revealed cerebellar tonsillar herniation of more than 6 mm below the foramen magnum ( Figure 2). This allowed us to diagnose CMI in the patient.  Spine MRI: The radiological survey of the cervical and thoracic spine showed no abnormalities. However, T1-and T2-weighted MRI scans of the cervical and thoracic spine showed a large singular syrinx, spreading in the cervicothoracic cord from C2 to Th12. The syrinx is more expanded between the cervical segments of C5 and Th1 ( Figure 3) and between thoracic segments of Th3 and Th7 ( Figure 4). Anteroposterior diameter of the syrinx at C5 was 16.3 mm ( Figure 5) and at Th6 was 12.6 mm ( Figure 6), while the anteroposterior diameters of the spinal cord at C5 and Th 6 were 19.8 and 15.3 mm, respectively.             In addition to changes in the structure of the spinal cord, coronal sections revealed signs of moderate curve 'S'-shaped scoliosis. In the thoracic region, the scoliotic curve bends to the left by 27 degrees, and in the cervical region, the scoliotic curve bends to the right by 20 degrees (Figure 7), which is a characteristic feature for Syr. As we know, the development of scoliosis in such patients may be associated with denervation of the paraspinal muscles [33,34].
In addition to changes in the structure of the spinal cord, coronal sections revealed signs of moderate curve 'S'-shaped scoliosis. In the thoracic region, the scoliotic curve bends to the left by 27 degrees, and in the cervical region, the scoliotic curve bends to the right by 20 degrees (Figure 7), which is a characteristic feature for Syr. As we know, the development of scoliosis in such patients may be associated with denervation of the paraspinal muscles [33,34].

Evoked Electromyography
In the upper extremities: motor and sensory nerve conduction and various F-response parameters have been examined in the median and ulnar nerves bilaterally. Distal latency and motor conduction velocity in the median and ulnar nerves were normal. Pronounced decrease of the compound muscle action potential (CMAP) was recorded on examination of the right median and ulnar nerves to 0.09 mV and 0.01 mV, respectively, and moderate decrease of the CMAP was registered on examination of the left ulnar nerve to 3.0 mV ( Figure 8). The CMAP of the left median nerve was normal (CMAP > 5 mV).

Evoked Electromyography
In the upper extremities: motor and sensory nerve conduction and various F-response parameters have been examined in the median and ulnar nerves bilaterally. Distal latency and motor conduction velocity in the median and ulnar nerves were normal. Pronounced decrease of the compound muscle action potential (CMAP) was recorded on examination of the right median and ulnar nerves to 0.09 mV and 0.01 mV, respectively, and moderate decrease of the CMAP was registered on examination of the left ulnar nerve to 3.0 mV ( Figure 8). The CMAP of the left median nerve was normal (CMAP > 5 mV). . The motor conduction velocity of the ulnar nerves: (a) motor conduction velocity of the left ulnar nerve below the elbow (V1) and above the elbow (V2), and the compound muscle action potential in response to stimulation at the wrist (A1), below the elbow (A2) and above the elbow (A3); (b) motor conduction velocity of the right ulnar nerve below the elbow (V1) and above the elbow (V2), and the compound muscle action potential in response to stimulation at the wrist (A1), below the elbow (A2) and above the elbow (A3). Blue arrows show compound muscle action potential amplitude and red arrows show conduction velocity.
Sensory nerve conduction velocity and sensory nerve action potential (SNAP) amplitude in the bilateral median and ulnar nerves were normal (Figure 9). The motor conduction velocity of the ulnar nerves: (a) motor conduction velocity of the left ulnar nerve below the elbow (V1) and above the elbow (V2), and the compound muscle action potential in response to stimulation at the wrist (A1), below the elbow (A2) and above the elbow (A3); (b) motor conduction velocity of the right ulnar nerve below the elbow (V1) and above the elbow (V2), and the compound muscle action potential in response to stimulation at the wrist (A1), below the elbow (A2) and above the elbow (A3). Blue arrows show compound muscle action potential amplitude and red arrows show conduction velocity. Sensory nerve conduction velocity and sensory nerve action potential (SNAP) amplitude in the bilateral median and ulnar nerves were normal ( Figure 9). left ulnar nerve below the elbow (V1) and above the elbow (V2), and the compound muscle action potential in response to stimulation at the wrist (A1), below the elbow (A2) and above the elbow (A3); (b) motor conduction velocity of the right ulnar nerve below the elbow (V1) and above the elbow (V2), and the compound muscle action potential in response to stimulation at the wrist (A1) below the elbow (A2) and above the elbow (A3). Blue arrows show compound muscle action poten tial amplitude and red arrows show conduction velocity.
Sensory nerve conduction velocity and sensory nerve action potential (SNAP) ampli tude in the bilateral median and ulnar nerves were normal ( Figure 9). In the lower extremities: motor and sensory nerve conduction velocities, CMAP am plitude, SNAP amplitude and various F-response parameters of the bilateral peroneal and tibial nerves were normal. Sural nerves studies showed normal conduction velocities and normal SNAP amplitude bilaterally. In the lower extremities: motor and sensory nerve conduction velocities, CMAP amplitude, SNAP amplitude and various F-response parameters of the bilateral peroneal and tibial nerves were normal. Sural nerves studies showed normal conduction velocities and normal SNAP amplitude bilaterally.
At rest, pronounced spontaneous activity was registered, such as fibrillation potentials, positive sharp waves (Figure 10), and fasciculation potentials ( Figure 11) in the right abductor pollicis brevis muscle, bilateral abductor digiti minimi, and bilateral first dorsal interosseous muscle of the hand. Rare fibrillation, positive sharp waves, and fasciculation potentials waves were registered on bilateral examination of the deltoid muscle, biceps brachii muscle, and brachioradialis muscle and in the left abductor pollicis brevis muscle.
In muscles, the f hands firing rate, frequency, and amplitude of positive sharp waves and fasciculation potentials were markedly higher on the left side. tials, positive sharp waves (Figure 10), and fasciculation potentials (Figure 11) in the right abductor pollicis brevis muscle, bilateral abductor digiti minimi, and bilateral first dorsal interosseous muscle of the hand. Rare fibrillation, positive sharp waves, and fasciculation potentials waves were registered on bilateral examination of the deltoid muscle, biceps brachii muscle, and brachioradialis muscle and in the left abductor pollicis brevis muscle.
In muscles, the f hands firing rate, frequency, and amplitude of positive sharp waves and fasciculation potentials were markedly higher on the left side.   At rest, pronounced spontaneous activity was registered, such as fibrillation potentials, positive sharp waves (Figure 10), and fasciculation potentials (Figure 11) in the right abductor pollicis brevis muscle, bilateral abductor digiti minimi, and bilateral first dorsal interosseous muscle of the hand. Rare fibrillation, positive sharp waves, and fasciculation potentials waves were registered on bilateral examination of the deltoid muscle, biceps brachii muscle, and brachioradialis muscle and in the left abductor pollicis brevis muscle.
In muscles, the f hands firing rate, frequency, and amplitude of positive sharp waves and fasciculation potentials were markedly higher on the left side.   Motor unit potential (MUP) analysis at slight voluntary muscle contraction revealed a significant increase in amplitude, duration, and size index of the MUP in the right abductor pollicis brevis muscle, right abductor digiti minimi, and right first dorsal interosseous muscle of the hand. MUP recruitment markedly reduced. The index of polyphasic MUP averaged 65%. In the left abductor digiti minimi and left first dorsal interosseous muscle of the hand, the amplitude, duration, and size index of the MUP were slightly enlarged, MUP recruitment was normal, and 25% polyphasic MUP was recorded. No significant changes were found on bilateral examination of the deltoid muscle, biceps brachii muscle, and brachioradialis muscle.
These changes suggest neurogenic abnormalities such as chronic denervation and re-innervation with acute denervation activity in the right abductor pollicis brevis muscle, bilateral abductor digiti minimi, and bilateral first dorsal interosseous muscle of the hand. Results indicate damage to the anterior horns of the spinal cord at the level of the C6-Th1 segments with loss of motor axons of the right median and ulnar nerves.
Quantitative needle EMG was performed in the tibial anterior, gastrocnemius, and vastus lateral muscles in the lower extremities bilaterally. These findings suggest the absence of abnormality in the investigated nerves and muscles of lower extremities and in the anterior horns of the spinal cord at the level of the L1-S2 segments.
Moreover, we examined the spontaneous activity in the tongue and rectus abdominal muscle. We did not record any fibrillation potentials, positive sharp waves, or fasciculation potentials at all.

Discussion
A 23-year-old Caucasian male with no significant past medical history presented to the Clinic of Brain and Vertebral Diseases (Moscow region, Russia) with atrophy and weakness of the small muscles of the right hand and moderate weakness of the left wrist. Symptoms appeared 4 years ago with initial weakness and hypotrophy in the right hand with a gradual increase in weakness in the left hand without any sensory loss. Moderate claw hand deformity of the right hand had developed. Bilateral fasciculations of the hands were visualized. Due to these symptoms, ALS was suspected. Impairment of the UMN was excluded, because the patient had no pathological reflexes, and periosteal and deep tendon reflexes in the upper and lower extremities were normal (except mild decrease of brachioradialis, elbow flexion, and triceps reflexes).
Findings on brain MRI revealed that the cerebellar tonsillar descended by 6 mm under the Mc-Rae line, which is typical for CM1. On spinal MRI, a syringomyelia was observed, which was formed by one huge singular syrinx. The syrinx originated from the C2 vertebra to the Th12 vertebra. The anteroposterior diameter of the syrinx had a maximum dilation at the C5-C7 and Th3-Th7 levels and reached 16.3 mm and 12.6 mm, respectively. Based on the clinical, neurophysiological, and MRI investigations, we came to the conclusion that neurological disorders were due to impairment of the anterior horns of the spinal cord at the C6-Th1 level. The impairment developed as a result of chronic motoneuron compression by the dilated syrinx at this region. The presence of CM1 on brain MRI was the basis for considering CM1-related Syr.
Neurophysiological findings of evoked EMG and conventional needle EMG were most likely due to damage to the anterior horns of the spinal cord at the C6-Th1 level predominantly in the right side. Therefore, the differential diagnosis of Syr-associated ASL mimic syndrome in the patient with CM1 was carried out with other disorders ( Table 2). Table 2. Differential diagnosis of syringomyelia-associated amyotrophic lateral sclerosis mimic syndrome in the patient with Chiari malformation type 1.

Disorder Clinical Findings MRI Findings Pathogenesis
Cervical myelopathy [35] Neck pain, hand numbness and paresthesia, loss of fine dexterity, amyotrophy and weakness of both the upper and the lower limbs, gait difficulties, Lhermitte's phenomenon, and sphincter incontinence.
Intramedullary signal abnormalities due to edema and structural changes with a hyperintense signal on T2-weighted MRI ( Figure 12) Compression of the spinal cord by spondylotic changes.

Disorder Clinical Findings MRI Findings Pathogenesis
Cervical spondylotic amyotrophy [36] Slowly progressive amyotrophy with weakness of the proximal extremity of one or both upper limbs, often preceded by a transient period of shoulder pain without sensory loss Narrowed intervertebral space between the vertebras of the cervical level. Sagittal T2-weighted magnetic resonance image showing root compression and impingement against prolapsed cervical discs Isolated intradural compression of multiple motor roots, without damage to either the spinal cord or the sensory roots.
Hirayama disease [37] Predominantly unilateral upper extremity weakness and atrophy, cold paresis, and no sensory or pyramidal tract involvement. It is also characterized by muscle weakness and atrophy in the hand and forearm with sparing of the brachioradialis, giving the characteristic appearance of oblique amyotrophy that affects the C7, C8 and T1 myotomes. The amyotrophy is unilateral in most patients, asymmetrically bilateral in some and rarely symmetric. Multifocal motor neuropathy [38,39] The pattern of weakness may be related to specific nerves. Due to the development of paresis as a result of conduction block, a high degree of weakness does not correlate with moderate muscle atrophy. Sensory disturbances could not be detected. Often recognized in patients with a short disease duration.
In EMG complex unstable MUPs without spontaneous activity at rest. Rapid recruitment pattern disproportionate to muscular atrophy. Fasciculation potentials may be recoded.

No specific changes on MRI
Chronic progressive immune-mediated motor neuropathy, which leads to progressive asymmetric weakness and partial motor conduction block in EMG. Anti-GM1 antibodies are identified in at least 40% of patients.
Idiopathic ALS [40,41] Progression of lower motor neuron signs (including EMG features in clinically unaffected muscles) and upper motor neuron signs, muscle atrophy, paralysis, frontotemporal dementia with absence of sensory signs. EMG is characterized by fasciculations in one or more regions, neurogenic changes, normal motor and sensory nerve conduction and absence of conduction blocks.
Bilateral symmetric T2 and FLAIR hyperintensities of the corticospinal tract. Decrease of cerebral volume in the gray matter of the frontal and temporal lobes. Gliosis and axonal degeneration of the anterolateral spinal cord, manifested by T1 hyperintensity and T2 hyperintensity.
The pathogenesis of ALS is still unknown. Mitochondrial dysfunction in cells leads to serious disorders associated with pathological changes in ALS, such as disturbances in the calcium buffer period, excessive formation of free radicals, which leads to an increase in mitochondrial membrane permeability and oxidative stress.

Disorder Clinical Findings MRI Findings Pathogenesis
The flail arm syndrome [42] Slow progressive, predominantly proximal weakness, and atrophy of the upper limbs. Symptoms may be limited to the cervical region without functional involvement of the lower extremities, pectorals, or bulbar muscles for at least 12 months. more regions, neurogenic changes, normal motor and sensory nerve conduction and absence of conduction blocks. manifested by T1 hyperintensity and T2 hyperintensity.
which leads to an increase in mitochondrial membrane permeability and oxidative stress.
The flail arm syndrome [42] Slow progressive, predominantly proximal weakness, and atrophy of the upper limbs. Symptoms may be limited to the cervical region without functional involvement of the lower extremities, pectorals, or bulbar muscles for at least 12 months. Five patients out of 10 develop signs of the UMN in the upper extremities and 7 patients out of 10 in the lower extremities.
Same as ALS Involvement of the corticospinal tract in Flail arm syndrome is identical to that in the patients with 'classic' ALS. Flail arm syndrome had a pattern of microstructural alterations in corticofugal tracts identical to those seen in ALS. Because of that there is a hypothesis that flail arm syndrome is such a phenotype of ALS. On differential diagnosis, cervical myelopathy was excluded due to the absence of impairment of the UMN in the lower extremities. Cervical spondylotic amyotrophy was excluded because of the absence of radicular compression on cervical spine MRI. Muscular atrophy in clinical cases did not appear similar to oblique amyotrophy associated with Hirayama disease. In addition, normal T2-weighted signals of the spinal cord on MRI at the site of the maximum forward shift in the cervical level led to the exclusion of Hirayama disease.
The absence of conduction blocks of motor nerves in EMG and correlated weakness with severity of muscle atrophy were the reason to exclude multifocal motor neuropathy.
According to the El Escorial criteria, the evidence of lower motor neuron degenera- On differential diagnosis, cervical myelopathy was excluded due to the absence of impairment of the UMN in the lower extremities. Cervical spondylotic amyotrophy was excluded because of the absence of radicular compression on cervical spine MRI. Muscular atrophy in clinical cases did not appear similar to oblique amyotrophy associated with Hirayama disease. In addition, normal T2-weighted signals of the spinal cord on MRI at the site of the maximum forward shift in the cervical level led to the exclusion of Hirayama disease.
The absence of conduction blocks of motor nerves in EMG and correlated weakness with severity of muscle atrophy were the reason to exclude multifocal motor neuropathy.
According to the El Escorial criteria, the evidence of lower motor neuron degeneration on clinical and neurophysiological examination of the cervical region and progressive spread of symptoms within one region, but not to other regions, was not enough to diagnose ALS. That is because the presence of clinical disorders of the upper motor neurons is the minimum requirement to diagnose possible ALS [43]. The flail arm syndrome and idiopathic ALS were excluded.
As a result, on the basis of the MRI findings and characteristic changes in evoked and needle EMG, Syr-associated ALS mimic syndrome with CM1 was diagnosed in our patient.
We searched for similar clinical cases in the literature using the PubMed-indexed journals search system. The criteria of search were as follows: Syringomyelia, Chiari Malformation I Type, an Amyotrophic lateral sclerosis. Among 2353 studies, 12 studies about 17 cases met the eligibility criteria (Table 3).
Thus, the lesion of only the LMN was demonstrated by the authors in just 7 cases. This indicates the extreme rarity of the development of isolated LMN lesions, without UMN impairment, in Syr-associated ALS mimic syndrome related with CM1. In our opinion, the predominant lesion of the anterior horns of the spinal cord because of compression by a syringomyelic cyst in our patient is most likely associated with a decrease in the resistance of these structures to compression and ischemia compared to the surrounding spinal cord tissue. In addition, the absence of a lesion of the UMN on an examination of the lower extremities indicates a high plasticity of the pyramidal pathways, despite pronounced syringomyelic changes in the spinal cord throughout between the C2 vertebra to the Th12 vertebra.
The nature of the work may be related to risk factors for the development of symptoms of Syr-associated ALS related with CM1, as the driver of a vehicle such as a bus is subjected to vibration and shaking for 6 hours 5 days a week. Obviously, prolonged and frequent mechanical stress on the spine and cranio-vertebral junction may adversely affect the morphological, neurophysiological, and clinical manifestations of Syr and ALS in patients with CM1. On the other hand, clinical cases of CM1-related ALS among bus drivers are not common in the literature [56].    Severe weakness: Strength in the proximal muscles was 0/5 points and 0/5 points in the distal muscles. Severe atrophy of the bilateral forearm flexor and extensor muscle groups. Atrophy and weakness of the shoulder abduction and intrinsic hand muscles more on the left hand than in the right hand.
Normal EMG studies showed chronic denervationreinnervation in C5 to C7 muscles bilaterally and in C8 muscles on the left Left side S > D LMN Note: F-female; M-male; M/age-manifestation age; Cl/age-clinical examination age; S-left side, R-right side; ALS-amyotrophic lateral sclerosis; EMG-electromyography; LMN-lower motor neuron; UMN-upper motor neuron; MNI-motor neuron impairment; CMAPs-compound muscle action potentials; SNAPs-sensory nerve action potentials.

Conclusions
CM1-related Syr may be the cause of the development of ALS mimic syndrome as a result of prolonged compression and ischemia of the anterior horns of the spinal cord. Our clinical case demonstrates that ALS mimic syndrome may be rare clinical disorder in patients with CM1-related Syr, while the characteristic symptoms for Syr are clinically absent or minimal.
A complex approach is needed to diagnose these disorders, including MRI of the head and spine, as well as induced evoked and needle EMG.

Declaration of Patient Consent
The authors confirm that they have obtained all necessary patient consent forms. In the form, the patients gave their consent for the publication of their images and other clinical information in the journal. The patients understand that their names and initials will not be published and appropriate steps will be taken to conceal their identity, but anonymity cannot be guaranteed. Informed Consent Statement: Written informed consent has been obtained from the patients to publish this paper.