Spontaneous conus infarction with "snake-eye appearance" on magnetic resonance imaging: A case report and literature review

Table 2 Identification of common diseases related to snake eye sign

Disease	Clinical features	Magnetic resonance performance	Neuroelectrophysiological manifestations
Conus medullaris infarction[38]	The main manifestations are sensory disturbance in the sellar region, bladder and rectal incontinence, bulbar anal reflex weakening or disappearing, erectile dysfunction, root neuralgia and lower limb motor neuron paralysis when combined with cauda equina damage	T12-L1 horizontal magnetic resonance T2WI and DWI high signal, T1W1 low signal	There are few reports about the neurophysiological characteristics of conus medullaris infarction. The reappearance of F wave after infarction may mark the improvement of clinical prognosis
Hirayama disease[39]	The self-limited disease, which is mainly characterized by unilateral muscle atrophy of the distal end of the upper limb, mainly affects the intrinsic muscles of the hand and forearm muscle groups. Typical clinical manifestations also include "cold paralysis", "finger extension tremor" and "muscle bundle tremor"	Asymmetric cervical spinal cord flattening, atrophy and intramedullary T2W1 high signal in cervical flexion position, disappearance of cervical physiological flexion, expansion and increase of epidural venous plexus, and anterior displacement of dural sac after over-extension and over-flexion position	The neurogenic damage of the affected muscle group mainly occurred in the C7-8 sarcomere and T1 sarcomere, while the C5-6 sarcomere (i.e. deltoid, biceps brachii and radial brachii) was not affected
Amyotrophiclateralsclerosis[34]	Malignant degenerative motor neuron disease characterized by multiple or localized progressive muscular atrophy and apraxia is characterized by limb spasms, tendon hyperreflexia, localized or multiple muscle weakness, muscular atrophy and fascicular tremor	T2WI, FLAIR and DWI can find symmetrical high signal in the pyramidal tract of the brain. In a few patients, SWI can see the deposition of hemosiderin along the motor cortex	The muscles innervated by different nerve segments of medulla oblongata, neck, chest and lumbosacral appear progressive denervation and chronic nerve regeneration
Cervical spondylotic myelopathy[40]	Based on cervical degeneration, the main manifestation is atrophy of the proximal or distal muscles of the upper limb, which usually occurs in one side, usually without sensory abnormalities	It is usually manifested as spinal cord thinning, intervertebral disc protrusion or prolapse. Due to long-term compression of the spinal cord, venous hyperemia and infarction can be caused, which can be secondary to cystic necrosis of the anterior horn of the spinal cord, forming T2WI snake-eye sign	Segmental neurogenic damage consistent with the distribution of the injured nerve root
Spinal muscular atrophy syndrome[41]	The most common autosomal recessive disease in childhood is progressive and symmetrical weakness and atrophy of limbs and trunk muscles	Anterior horn of spinal cord α- Degeneration and degeneration of motor neurons led to T2WI snake-eye sign	Typical neuronal damage, fiber fibrillation wave and positive sharp wave can be seen at rest, bundle fibrillation potential can be seen occasionally, and regular spontaneous motor unit activity potential is the characteristic manifestation of its EMG

DWI: Diffusion-weighted imaging; EMG: Electromyography; FLAIR: Fluid-attenuated inversion-recovery; SWI: Susceptibility weighted imaging; T2WI: T2-weighted imaging.