Bilateral thoracic disc herniation with abdominal wall paresis: a case report

We present a rare case of a patient initially presenting with unilateral abdominal wall bulging and radicular pain caused by a lateral disc herniation at Th11/12, later suffering from a hernia recurrence with bilateral disc prolapse and motor deficits. The patient underwent sequesterectomy via a right hemilaminectomy at Th11, and after 8 weeks, a bilateral sequesterectomy with semirigid fusion Th11/12 was performed. Unilateral motor deficits at the thoracic level have been discussed in case reports; a bilateral disc protrusion with abdominal wall bulging occurring as a recurrent disc herniation has never been described before.


Physical examination results
Except for the right abdominal wall bulging and radicular pain projecting on the Th11 nerve root, no focal neurological deficit could be detected. There were no clinical signs of myelopathy, no burdening back pain, no bladder or sphincter dys-function, and no gait impairment. Reflexes were minimally prominent on the right side due to the history of a left stroke.

Imaging
At the initial presentation at the general and visceral surgical department, the patient underwent computer tomography (CT) of the abdomen. An abdominal wall hernia was excluded (Fig. 2). After neurological examination, an MRI of the thoracic and lumbar spine was performed, showing a large disc prolapse at the Th11/12 level on the right side affecting the right Th11 nerve root (Fig. 3).

Electrophysiology
Needle electromyography (EMG) of the right-sided Th11 paravertebral muscles 8 days after onset revealed fibrillations as a sign of florid denervation, indicating acute Th11 nerve root compression.   The MRI scan of the thoracolumbar spine T2 weighted axial and sagittal presents a rightsided disc herniation TH 11/12

Surgical treatment
Due to the acute denervation and persistent pain symptoms, the disc herniation was removed 6 days after symptom onset through a Th11 hemilaminectomy on the right side with intraoperative X-ray control.

Outcome and second operation
The patient was discharged on the second postoperative day with moderate wound pain and complete resolving of the abdominal radicular pain. The abdominal wall bulging did not resolve.
After 8 weeks, the patient presented in the outpatient department with a new sudden onset of abdominal bulging occurring on the left side (symmetrical to the already existing right wall bulging: Fig. 4). The MRI revealed a recurrent disc prolapse at the operated Th11/12 level-now on both sides and accentuated on the right side-as well as a degeneration of the Th11/12 Modic type I disc, matching the clinical symptoms of the patient (Fig. 5). EMG of the left-sided Th11 paravertebral muscles 4 days after the onset of left abdominal wall paresis was normal, probably because of too early an examination.
Due to the already performed hemilaminectomy on the right side and the symptoms of segmental instability, the patient was advised to have an operative treatment with discectomy and Th11/12 dynamic fusion with a semirigid (Cosmic MIA, Ulrich) instrumentation (Figs. 6 and 7). Back pain resolved after the operative treatment; the bilateral abdominal wall bulging remained stable (follow-up 5 months).

Discussion and conclusions
Diagnostic pathway Important differential diagnoses include thoracic diabetic radiculopathy [10], herpes zoster infection [18], abdominal malignancies, prior laparoscopic or minimally invasive surgeries [3,22], and abdominal wall hernia and can lead to a swelling and bulging of the abdominal wall with radiating thoracic pain. These entities were considered and excluded via a paraspinal EMG and a CT scan. An MRI scan was performed leading to the diagnosis of thoracic disc herniation. In fact, patients may confound the abdominal pain with visceral pathologies, which is more common than disc prolapses causing the symptoms. The diagnostic pathway is indeed explainable, as symptomatic thoracic disc herniation is rare, accounting for only 0.25-0.57% of all disc herniation [24], and is more commonly above the level TH8 [24]. A further supplementary diagnostic method performed in this case was the EMG, showing signs of monosegmental nerve root compression [11].

Initial surgical procedure
There are several possible surgical approaches to treat thoracic disc herniation, depending on localization, calcification of the  herniated disc, and segmental instability. Posterolateral approaches are recommended for soft lateral disc herniation [8], and the transthoracic approach is more commonly used in large calcified central hernia [11]. Whether to stabilize or to perform a discectomy at all is currently a matter of debate [13,21,23]. Instrumented fusion can be required in cases performed from the posterior [11]. As our patient initially presented with an acute unilateral soft disc herniation without signs of segmental instability, we opted for a posterior approach with instrumentation.

Recurrent disc herniation
Less data is available on the recurrence rate of thoracic disc herniation. The general rate of recurrent disc herniation has been reported between 0.5-25%, especially in the first months after a successful first surgical procedure [5], but describes only recurrent disc herniation in the lumbar spine. Some of the common possible risk factors are obesity, smoking, male gender, diabetes, weightlifting, the size of the annular tear, and type of primary operation [5].
Surgical procedure after recurrent disc herniation Currently, we lack guidelines with significant comparative studies for the surgical treatment of recurrent disc herniation. In a systematic review comparing possible treatments after recurrent lumbar disc herniation [5], excellent outcomes were described for re-discectomies, posterolateral fusion, and posterior lumbar interbody fusion (PLIF) without significant differences between the applied options.
Dower et al. found similar rates of satisfactory outcomes in patients undergoing discectomy alone versus discectomy with fusion (79.9% vs. 77.8%, respectively) but stated significant improvements in back pain scores in patients undergoing fusion compared with isolated discectomy (60.1% vs. 47.2%, respectively) [4]. Currently, many surgeons advocate for rediscectomy alone in cases without deformity, instability, or associated back pain and opt for instrumented fusion if one of the symptoms is present [19].

Patient outcome
The clinical outcome after disc or recurrent disc herniation is dependent on several factors, such as the time between first symptoms to surgical approach, size, and location of disc herniation, and preoperative clinical status. Most studies focus on the clinical outcome in myelopathic patients [8], and we currently lack sufficient data describing regeneration of thoracic motor deficits. In our case, the abdominal wall bulging did not resolve after surgical treatment.

Conclusion
The patient showed a clear benefit from the two operations regarding the radicular and back pain, which were distinctly better than the pain was preoperatively. The motor deficit with the bilateral abdominal wall bulging remained stable. To our knowledge, unilateral abdominal wall paresis due to thoracic disc herniation has only been reported in four case reports; a bilateral disc protrusion with symmetrical abdominal wall  paresis has never been described before. We hereby present a unique and very rare case of motor deficits at the thoracic level without myelopathy, with diagnostic implications, surgical treatment, and clinical outcome.
Funding Open Access funding enabled and organized by Projekt DEAL.

Compliance with ethical standards
Patients Consent The patient has consented to the submission of the case report for submission to the journal.
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