Spinal intramedullary schwannoma: Report of two cases with review of the literature

Abstract

Introduction

Spinal tumors comprise 15 % of all central nervous system tumors, with schwannomas accounting for 30 % of primary intraspinal neoplasms. While predominantly extramedullary-intradural, spinal schwannomas rarely manifest intramedullary occurrences (0.3 % of intraspinal tumors). This study sheds light on two rare cases of thoracic intramedullary schwannomas, emphasizing their diagnostic complexities and surgical management, alongside a literature review.

Case presentation

Case 1 involves a 50-year-old female presenting with worsening back pain, right lower limb weakness, and urinary incontinence. MRI revealed an intradural intramedullary soft tissue mass, diagnosed as a schwannoma with an associated organizing hematoma. Surgical removal led to gradual improvement. Case 2 features a 25-year-old male with back pain, partial foot drop, and weakness in the right knee and hip. MRI demonstrated an intradural intramedullary lesion, later confirmed as an intradural intramedullary schwannoma. Surgery resulted in a smooth recovery without adverse effects.

Discussion

This article presents two cases of intradural intramedullary thoracic schwannomas initially misdiagnosed as astrocytomas. Surgical resection confirmed the diagnosis, underscoring challenges in preoperative MRI diagnosis. The review of 174 reported cases reveals an equal distribution between the cervical and thoracic regions, with males affected 1.5 times more frequently than females. The average age of onset is 40, and surgical treatment demonstrates a 90 % improvement rate. The complex pathogenesis encompasses six proposed explanations. Clinical suspicion, considering pain and neurological symptoms, is paramount due to potential misdiagnosis and the imperative for histological confirmation.

Conclusion

Although rare, intramedullary schwannomas (IMS) have significant clinical implications, necessitating precise treatment. Surgical resection yields favorable outcomes, with subtotal resection considered based on adhesion factors. Pre-surgical diagnosis requires a comprehensive integration of radiological and clinical data, with intraoperative analysis ensuring optimal treatment strategies.

Highlights

• •Intramedullary schwannomas (IMS) are rare, constituting 0.3 % of intraspinal tumors, challenging both diagnosis and surgical management.
• •The cases highlight the misdiagnosis of IMS as astrocytomas, emphasizing the necessity for precise preoperative MRI diagnosis and histological confirmation.
• •IMS distribution is equal in cervical and thoracic regions, affecting males 1.5 times more than females, with an average age of 40 years.
• •Surgical resection, with a 90 % improvement rate, remains the primary treatment for IMS; however, considering adhesion, subtotal resection could be a viable option.
• •Early diagnosis hinges on clinical suspicion, recognizing pain and neurological symptoms, necessitating a comprehensive approach integrating radiological and clinical data, and intraoperative analysis for optimal treatment.

1. Introduction

Spinal tumors account for approximately 15 % of all central nervous system tumors [1], with schwannomas comprising 30 % of all primary intraspinal neoplasms [2]. The majority of spinal schwannomas are extramedullary-intradural; however, in 10 % of cases, they may be extradural or exhibit a mixed intra-extradural presentation in 10–15 % of cases [1]. Intramedullary schwannomas (IMS) are rare, representing only 0.3 % of all intraspinal tumors and 1.1 % of all intraspinal schwannomas [3].

Schwann cells, the origin of schwannomas, are not present in the spinal cord, rendering intramedullary schwannomas uncommon and seldom reported in the literature. Magnetic resonance imaging (MRI) typically identifies them as intramedullary lesions, which are subsequently confirmed by biopsy following surgical resection. Here, we present two cases of thoracic IMS, one male and one female.

This work is also reported in line with SCARE criteria which helped to improve the transparency and quality of this case report [19].

2. Case presentation

2.1. Case 1

A 50-year-old female patient, with no history of hypertension or prior surgeries, presented to the emergency department with complaints of back pain, weakness in the right lower limb, and urinary incontinence. The onset of symptoms began five years ago with back pain, for which the patient sought consultation and was diagnosed with lumbar spondylosis, initiating medical treatment. While there was partial improvement initially, the condition worsened over the past year, with escalating back pain radiating to the right lower limb and accompanied by weakness. Despite seeking medical advice and treatment, there was no significant improvement. In the last 20 days, the symptoms deteriorated further, with increased weakness in the right lower limb and urinary incontinence, prompting the patient to seek further medical attention. Neuroimaging was performed prior to referral to our department.

Neurological examination revealed grade 4 motor power in the right lower limb and grade 5 in the left lower limb, with the sensory level opposite the umbilicus. Hypoesthesia in the saddle area, hyperreflexia, and pathological reflexes were also noted.

MRI findings revealed a well-defined, oblong-shaped intradural intramedullary soft tissue mass lesion with a small left posterolateral cystic component extending from the D9 to D11 levels, resulting in cord expansion, measuring approximately 48 × 19 × 13 mm. The lesion exhibited an isointense signal on T1-weighted images and an intermediate to high signal on T2-weighted images, with minimal heterogeneous post-contrast enhancement, as well as a bright signal from its cystic component on T2-weighted images. The bone marrow signal intensity in the examined lumbar and dorsal spines was normal, with normal neural canals at all levels and no paraspinal masses observed (Fig. 1).

Fig. 1.

Preoperative sagittal MRI T2 and T1 weighted images (a) and (b), respectively, and an axial T2 MRI (c).

Due to suspicion of a lower dorsal astrocytoma, the patient was scheduled for surgical removal. After obtaining informed consent and counseling, the operation was performed via D9 to D11 laminectomy, with excision of the intramedullary mass, which consisted of multiple small tissue fragments measuring approximately 4 × 3 cm each (Fig. 2).

Fig. 2.

Shows the gross picture of multiple small fragments of the resected schwannoma.

Post-surgery, the patient reported no new sensory or motor impairments, with gradual improvement observed. Histopathological examination revealed spindle cell proliferation, demonstrating alternating moderately cellular and low-cellular areas (Antoni A and Antoni B patterns), with serpentine nuclei detected. Component cells displayed mild cellular atypia with no identified mitoses. Focal areas of papillary endothelial hyperplasia with scattered hemosiderin-laden macrophages were also observed. There was no evidence of malignancy in the examined specimen. The histopathological findings were consistent with schwannoma with associated organizing hematoma (Fig. 3).

Fig. 3.

Histopathological findings of the schwannoma. (a) and (b) are 400 and 100 times magnified, respectively. (c) demonstrates the Antoni A and Antoni B tissue patterns.

2.2. Case 2

A 25-year-old male patient, with no significant medical history, presented to the emergency department complaining of back pain, a partial foot drop, and weakness in the right knee and hip movements. He had not previously sought medical attention for these symptoms. Neurological evaluation revealed grade 4 motor power in the knee and hip, with no signs of incontinence and intact sensation. However, hyperreflexia and loss of knee reflex were observed, while cranial nerves appeared normal.

MRI findings showed a well-defined, heterogeneous, solid intradural intramedullary lesion located opposite the D12 to L1 level. The lesion exhibited low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, with heterogeneous post-contrast enhancement (Fig. 4). Astrocytoma was suspected.

Fig. 4.

Preoperative sagittal MRI T2 and T1 weighted images (a) and (b), respectively, and an axial T2 MRI (c), all indicate intramedullary schwannoma.

Following informed consent and counseling, the patient underwent surgery via D12 to L1 laminectomy for intramedullary mass excision. Post-surgery, the patient experienced a smooth recovery with no adverse outcomes.

Histopathological examination revealed tumor tissue composed of spindle cells with wavy vesicular nuclei arranged in a fascicular pattern, with focal nuclear palisading. Alternating zones of hypercellularity and hypocellularity were observed, with no evidence of nuclear pleomorphism or mitotic activity. No malignancy was identified in the examined sections, consistent with a diagnosis of intradural intramedullary schwannoma (Fig. 5).

Fig. 5.

Histopathological findings of the schwannoma.

3. Discussion

In this article, we present two cases of intradural intramedullary thoracic schwannoma in a female and a male patient, located at the levels of D9 to D11 and D12, respectively. Both cases were initially misdiagnosed as astrocytomas, but surgical removal of the tumor confirmed the diagnosis of IMS through histological examination.

The most recent review in 2020 reported a total of 166 cases of IMS up to that point [4]. Additionally, six more IMS cases have been reported in the last three years, bringing the total number of reported cases, including ours, to 174 (Table 1). These cases demonstrate that IMS affects the cervical and thoracic regions equally, with the lumbar region showing the lowest prevalence. Males are 1.5 times more likely to be affected than females, with an average age of onset of 40 ± 16.9 years (median = 40.5). The average duration of symptoms is 21.8 months (median = 12.5), ranging from one month to 20 years. Surgical treatment was employed in all cases, with 90 % showing improvement [[5], [6], [7], [8], [9], [10]].

Table 1.

Summary of the previous similar case reports.

Study ID	Patient characteristics		Presentation			Symptoms duration (months)	Treatment	Preliminary diagnosis	Level of the tumor	Recovery
	Age	Gender	Pyramidal symptoms	Disturbed sensation	Urinary incontinence
Our study
Case 1	50	Female	Yes	Yes	Yes	60	Surgical removal	Astrocytoma	D9–D11	Improved
Case 2	25	Male	Yes	No	No	4	Surgical removal	Astrocytoma	D12–L1	Improved
Previous cases since the last review
Shahab et al. 2022	52	Male	Yes	No	No	1	Surgical removal	Ependymoma	D11	NA
Varshney et al. 2020	70	Male	Yes	Yes	Yes	30	Surgical removal	Ependymoma or astrocytoma	D11 to L2	Improved
Tahta et al. 2021	38	Male	No	No	No	1	Surgical removal	astrocytoma	Cervicomedullary junction	Improved
Decharin et al. 2022	63	Male	Yes	Yes	NA	60	Surgical removal	Astrocytoma or ependymoma	C4 to C6	Improved
Duvuru et al., 2023	23	Male	No	No	No	2	Surgical removal	Glioma	C2 to C3	Worsened
Dandpat et al. 2021	17	Male	Yes	Yes	Yes	6	Surgical removal	Astrocytoma	Medulla to C5	NA
Cases included in last systematic review (166 cases)
Swiatek et al. 2020	39.8 ± 16.86 (Median = 40.5)	Male (92) Female (74)	Yes (113) No (24)	Yes (112) No (25)	Yes (43) No (92)	Mean = 22 Median = 13	Surgical removal (All cases)	NA	Cervical (92) Thoracic (86)	Worsened (13) Improved (119)

The pathogenesis of intramedullary schwannoma has long been debated due to disagreements about its origin, as Schwann cells are lacking in the spinal cord. Several explanations have arisen to explain the development of IMS, and till now, six explanations have been retrieved from the literature: 1) Schwann cells originate in the CNS from the perivascular nerve plexus that surrounds blood vessels [11]. 2) During embryonic development, ectopic Schwann cells migrate and undergo late neoplastic progression [12]. 3) Pial mesodermal cells are transformed into neuroectodermal Schwann cells [13]. 4) As a result of faulty spinal cord regeneration following mechanical trauma or chronic disease [12]. 5) Schwann cells ensheathe abnormal intramedullary nerve fibres [14]. 6) Schwann cells form a tumor on a dorsal root at the critical area where the dorsal root loses its cover and enters the pia mater, which is sometimes referred to as “subpial schwannoma” [9].

Preoperative radiological diagnosis of IM schwannoma based solely on MRI findings is challenging. In our study, IMS findings on MRI were misdiagnosed as spinal astrocytoma, a consistent observation in the literature [5,8,15]. The IMS in our case was located in the thoracic region, a common site for astrocytoma [15]. A distinguishing feature of MRI is that IMS always exhibits enhancement, which may be a heterogeneous, homogeneous, circular, or minimal enhancement, whereas astrocytoma may not enhance at all [4,16]. This, however, is not the rule [16], and the only reliable diagnosis is a histological examination. In schwannomas, histological findings typically include two distinct spindle cells arranged in alternating zones of hypercellularity (Antoni A) and hypocellularity (Antoni B). In astrocytomas, histological examination reveals astrocytes, nuclear atypia, increased mitoses, microvascular proliferation, and/or necrosis [20].

Given that histological examination is the definitive diagnosis and misdiagnosis can lead to inappropriate treatment, a high level of clinical suspicion based on both radiological and clinical data is essential. The most common clinical manifestations include pain, either root or somatic, alone or in combination with pyramidal symptoms and/or sensory impairments, with sphincter dysfunction appearing later. In late stages, intramedullary tumors, including schwannoma, astrocytoma, and ependymoma, produce similar clinical manifestations. However, in the initial symptoms, schwannoma is usually manifested by somatic or root pain, while astrocytoma is usually manifested with motor weakness, and ependymoma is manifested with either paresthesia or somatic or root pain [21].

The correct diagnosis of IMS and its differentiation it from astrocytoma has significant implications for management. Schwannoma has a well-defined cleavage plane, making total resection feasible. Furthermore, IMS has a low recurrence rate after surgical removal (4 %), even after subtotal resection, which may be done in some cases with infiltrative IMS [1,4,17,18]. On the other hand, total resection of astrocytomas is impossible as it is usually infiltrative and has a high recurrence rate; therefore, surgical resection of astrocytomas should be followed by chemotherapy and radiotherapy [22,23]. Therefore, the appropriate diagnosis can have an impact on treatment. Intraoperative frozen section analysis can help confirm the diagnosis.

4. Conclusion

Intramedullary schwannomas (IMS) are uncommon occurrences. Total surgical resection is generally regarded as the optimal treatment option for IMS and often results in a favorable prognosis. However, in cases where there is strong adhesion, subtotal resection may be considered. Due to the challenge of establishing a definitive diagnosis prior to surgery, it is crucial to integrate radiological data, such as the presence of an intramedullary lesion with significant enhancement and a well-defined cleavage plane, with clinical data, including symptoms such as somatic or root pain, with or without motor deficits, sensory impairments, and/or sphincter dysfunction. Intraoperative frozen section analysis can assist in confirming the diagnosis and ensuring the most appropriate treatment approach.

Ethical approval

Ethics clearance was not necessary since the University waives ethics approval for publication of case reports involving no patients' images, and the case report is not containing any personal information. The ethical approval is obligatory for research that involve human or animal experiments.

Funding

N/A. We received no funding in any form.

Guarantor

The corresponding author takes the full responsibility of the work.

Registration of research studies

This case report is not a first time of reporting, new device or surgical technique. So I would not need a Research Registry Unique identifying number (UIN).

Consent of patient

Patient's consent was taken for publishing this case and the images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Provenance and peer review

Not commissioned, externally peer-reviewed.

CRediT authorship contribution statement

Hazem Mohamed Salamah: Validation, Writing – review & editing, Visualization, Methodology, Software, Writing – original draft, Formal analysis. Ahmed G. Eltokhy: Validation, Formal analysis, Writing – review & editing. Mohammad Ezzat: Validation, Formal analysis, Writing – review & editing. Ahmad Alkheder: Validation, Writing – review & editing, Visualization, Methodology, Software, Writing – original draft, Formal analysis. Mahmoud M. Taha: Supervision, Writing – review & editing, Project administration.

Declaration of competing interest

The Authors disclose no conflicts.

Data availability

All data are available from the corresponding author on reasonable request. The case has not been presented at a conference or regional meeting.