Hirayama and Granuloma—The Affinity Saga

Abstract

Foreign-body granulomas secondary to synthetic materials used in neurosurgery are common. It has been reported that most of them occur after brain surgery than spinal surgery. Hirayama disease, which presents as a slow progressive upper limb muscle weakness and subsequently atrophy, obligates surgical intervention when the conservative management fails. It is managed by posterior cervical surgery followed by dural repair, while anterior cervical surgery is also an option. The component present in duroplasty material, ReDura, may cause exuberant granuloma formation. Foreign-body granuloma at the site of dural repair secondary to the synthetic dural component can cause spinal cord compression worsening the symptoms, requiring surgery. We hereby report a case of a young male with Hirayama disease who underwent posterior cervical surgery followed by duroplasty. The mass effect by the granuloma, secondary to dural repair, was relieved surgically and patient improved neurologically.

 

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Keywords

Hirayama disease - granuloma formation - ReDura - posterior cervical techniques - MRI spine

Introduction

Monomelic amyotrophy, popularly known as Hirayama disease, is a neurological disorder causing asymmetric segmental muscular atrophy of the distal upper extremities commonly affecting young Asian males.[1] Characteristic clinical and dynamic magnetic resonance imaging (MRI) spine findings help diagnose the disease. Conservative management is offered for milder forms, while surgery is preferred for progressive disease. The two surgical approaches include anterior and posterior cervical techniques. The posterior cervical technique involves dural repair. The synthetic materials used for artificial dura can result in foreign-body granuloma. Only one case report has been published so far involving the spine and this included cervical spine.[2] There has been no other case report or series involving the spine till date. A series of cases have been published regarding the same following craniectomy.[3] The objective of the study is to outline the characteristic features and the complication of post-surgical granuloma in spine surgery in a patient with Hirayama disease.

 

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Case Report

A 19-year-old young male presented with history of progressive weakness of bilateral hands and associated reduced bilateral hand muscle bulk for 2 months. He complained of difficulty in writing and using hand for daily routine activities. He was unable to lift weights and had pain in bilateral hands. There was no history of trauma, spasticity, or lower limb involvement. On examination, he had bilateral symmetrical wasting and weakness of hand muscles flattened thenar and hypothenar eminences, involving right more than left with right hand grip weakness of 60 percent. Reflexes and sensations were normal. There was no other neurological deficit. In suspicion of Hirayama disease, dynamic MRI cervical spine was advised, which revealed anterior displacement of posterior dural with prominent posterior epidural fat on flexion from third cervical to first thoracic (C3 to T1) vertebral level along with subtle spinal cord signal changes at the C7–T1 level, confirming the same ([Fig. 1A]–[C]). He underwent C3–T1 laminectomy and bilateral lateral mass screw placement and duroplasty with ReDura under intraoperative neurophysiological monitoring. Intraoperative findings included epidural venous engorgement, thickened dura from C3 to C5 vertebrae. The patient was stable during the discharge and was advised cervical collar ambulation and limb physical therapy.

Fig. 1 Hirayama disease presurgical and post-surgical status. (A) Sagittal T2-weighted (wt) sequence of cervical spine in neutral position shows no significant abnormality. (B) Sagittal T2 wt sequence of cervical spine in flexion shows anterior displacement of the spinal cord with prominent posterior epidural flow voids (arrow). (C) Axial T2 wt sequence of cervical spine at the C7–T1 level reveals subtle hyperintense signal changes in the anterior column on both sides (arrow). (D and E) Sagittal T2 wt sequence showing linear thick hypointensity at the operative site over the ReDura compressing the spinal cord with signal changes at the T1–T2 level (arrows). (F) Axial T2 wt sequence showing T2 hypointensity at the C7–T1 level with cord signal changes (arrow).

After 6 months, the patient complained right anterior thigh sensory loss and numbness for 1 month, and difficulty in walking for 1 week. On examination, power of all the limbs was 5 out of 5, and sensation was reduced on right side below T10–L3 dermatomes. Ankle clonus was positive on both sides with spasticity in bilateral lower limbs and exaggerated bilateral knee jerks. Following this, MRI was advised, which revealed heterogeneously thickened linear T2 hypointensity at the operative site, anterior to the ReDura from C3 to T1 vertebral level with subtle spinal cord signal changes ([Fig. 1D]–[F]). There was also a T1–T2 disc bulge causing cord indentation and mild bilateral neural foraminal narrowing. Surgery was indicated to relieve the mass effect on the cord. T2 laminectomy was done along with excision of the granulation tissue over the previous duroplasty site. ReDura was also removed along with the granulation tissue. Duroplasty was done with fascia lata. Histopathology revealed exuberant granulomatous reaction with retractile foreign bodies, as well as fibroblastic and histiocytic proliferation ([Fig. 2A]–[D]). Post-surgery, his sensory loss improved and maintained the power of all the limbs. He was discharged in stable condition and has no complaints on follow-up. MRI was advised three months after the discharge. It showed residual spinal cord signal changes and no granuloma ([Fig 3A], [B]).

Fig. 2 (A and B) Intraoperative images showing granuloma (arrow) at the duroplasty site. (C and D) Microscopy showed mesh-like refractile foreign body, eliciting exuberant foreign-body granulomatous reaction with fibroblasts and histiocytes (arrows).

Fig. 3 (A and B) Sagittal and axial T2 wt sequences showing release of cord compression following removal of granuloma (arrows) with resolving cord edema at the T1–T2 level.

 

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Discussion

Hirayama disease is a disorder of the lower motor neurons involving the distal upper extremity muscles which gradually turn atrophic. This condition is seen commonly in the younger males and may involve cervical or thoracic spine.[3] The most common site is at the C7–T1 level.

An insidious onset of upper limb weakness and wasting, commonly involving the ulnar forearms and intrinsic muscles of the hand, is the most common presentation, although occasionally proximal upper limb involvement has been reported. Patients may also present with tremors.

There are several factors that contribute to the disease process, including asymmetrical growth of the spinal canal and cord in puberty, anterior displacement of the spinal cord reducing blood flow through the anterior spinal artery due to compression by the posterior cervical vertebrae, engorged venous plexus in the posterior epidural space, shortened cervical roots, or dynamic instabilities in patients with long necks.[4]

Electrophysiological findings in Hirayama disease include F wave with normal latency but reduced frequency and conduction velocity. Changes in the somatosensory and motor-evoked potentials have been documented.[5]

MRI is the modality of choice to confirm the disease by obtaining flexion and neutral views. The forward displacement of the posterior dura is diagnostic of the disease. Flattening of the spinal cord and an increase in the laminodural space are the characteristic imaging findings, demonstrated on the flexion view.[6] Other features are straightening of the cervical spine, prominent posterior epidural flow voids, and post-contrast crescent-shaped posterior enhancement during flexion. The popular “snake eye appearance” on MRI spine indicates permanent disaster, and is due to ischemia or necrosis of the anterior horn cells.[7] Thinning and flattening of the cord are also characteristic.

While cervical collars are the initial treatment for the condition and require a longer period of treatment, surgery is recommended to stop disease progression, to decompress the spine, and to correct the alignment of the cervical spine.

Anterior and posterior cervical surgeries are the two known approaches used in Hirayama disease. Anterior cervical surgery includes anterior cervical discectomy and fusion or corpectomy decompression and fusion. Posterior cervical surgery involves posterior fusion/fixation of C1–C6/C7 vertebrae or laminectomy/laminoplasty with duroplasty.[8] Duroplasty is done to prevent the displacement of the spinal cord compressing against the vertebral bodies anteriorly as the diseased patients may have ectatic dura with loss of elasticity.[9] The synthetic dura is used in duroplasty to repair the dural defects. Many such synthetic durae are available at present and may result in foreign-body reactions. The contents of the duroplasty material used in our study contained poly-L-lactic acid with a trade name of ReDura, which is used widely. It is manufactured based on biomimetic electrospun technology and has hydrophobic surface property, preventing cerebrospinal fluid (CSF) leakage.[10]

Extensive foreign-body reactions have been documented using ReDura in a case series of post-decompressive craniectomy patients.[11] Initiation of inflammatory response by the giant cells results in granuloma formation. Initially, there is acute inflammation by mast cells, followed by chronic inflammation by mononuclear cells, limited to the foreign-body site resulting in foreign-body giant cell formation, responsible for granuloma.[12] It appears T1 and T2 hypointense without diffusion restriction with intense homogeneous enhancement. The granuloma formed over the duroplasty if extensive can sometimes appear as a thick mass, resulting in the adjacent spinal cord being affected by the mass effect. On histology, such foreign-body granuloma is seen as a background of dense connective tissue with crystal-like/retractile structures surrounded by multinucleated giant cells and lymphocytes.

Despite the fact that the granuloma formation helps prevent CSF leaks in dural repair surgery, foreign-body granuloma may need to be treated surgically to combat any underlying mass effect, particularly on the spinal cord.

 

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Conclusion

Surgery is necessary in Hirayama disease to halt the disease progression. Posterior cervical surgery accompanied with duroplasty to repair the dural defect may result in exuberant granuloma formation due to the synthetic material used. MRI scan helps diagnosing the condition. Awareness of the foreign-body reaction to duroplasty materials is important and re-surgery may be necessary to reverse the mass effect.

 

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Conflict of Interest

None declared.

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Publication History

Article published online:
01 July 2025