Isolated pontomedullary hydatid cyst presenting with progressive bulbar and long-tract dysfunction: a case report and literature review

Abstract

Background

Intracranial cystic echinococcosis is rare, and primary involvement of the brainstem is exceptional. Because brainstem cystic lesions often share overlapping clinical and radiological features, preoperative diagnosis may be challenging, particularly when the lesion is deep-seated and located near critical bulbar and long-tract pathways.

Case presentation

A 47-year-old woman from a rural area presented with a 4–6-week history of progressive dysphagia and worsening weakness of all four limbs. Neurological examination revealed quadriparesis and lower cranial nerve dysfunction, including dysphonia, reduced gag reflex, and mild palatal asymmetry. Brain magnetic resonance imaging revealed a solitary, sharply demarcated intra-axial cystic lesion at the pontomedullary junction, with cerebrospinal fluid–like signal intensity, suppression on fluid-attenuated inversion recovery sequences, a thin regular wall, and no enhancement, mural nodule, calcification, or perilesional edema. Systemic evaluation showed no extracranial hydatid involvement. Given the epidemiological background and imaging pattern, a pontomedullary hydatid cyst was suspected. The narrow brainstem corridor made standard hydrodissection unsuitable, so, the patient underwent left lateral suboccipital craniotomy. Controlled cyst puncture and aspiration were performed to decompress the lesion, followed by meticulous microsurgical removal of the collapsed cyst wall without intradural spillage. Histopathology confirmed hydatid disease. The postoperative course was uncomplicated, with marked improvement of limb strength and marked recovery of swallowing function. Follow-up MRI showed complete excision without residual lesion, hydrocephalus, diffusion restriction, or mass effect.

Conclusion

Hydatid disease should be considered in the differential diagnosis of well-circumscribed, non-enhancing cystic brainstem lesions, particularly in patients from endemic settings. This case highlights the value of combining neuroimaging findings with epidemiological context to raise preoperative suspicion, and illustrates the need for individualized microsurgical planning in eloquent pontomedullary locations where standard hydrodissection may be unsafe or impractical.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12883-026-05179-8.

Background

Hydatid disease (cystic echinococcosis) is a zoonotic parasitic infection caused by the larval stage of tapeworms of the genus Echinococcus. It represents a significant global health problem, particularly in endemic regions, including the Middle East, Mediterranean countries, Central Asia, and South America, and is more prevalent in rural and pastoral communities, where livestock farming and close contact with dogs play a key role in the parasite life cycle. Humans acquire the infection through ingestion of parasite eggs from contaminated sources, or through direct contact with definitive hosts, most commonly dogs, thereby acting as accidental intermediate hosts in the parasite life cycle [1, 2].

The liver and lungs are the most frequently affected organs; however, other organs such as the kidneys, bones, and central nervous system may also be involved [2].

Central nervous system involvement is infrequent, accounting for approximately 1–2% of all hydatid disease cases and a comparable percentage of all intracranial space-occupying lesions. The majority are supratentorial within the distribution of the middle cerebral artery (MCA) predominantly involving the parietal lobe, whereas deep-seated locations, such as the brainstem, remain highly unusual. Despite its rarity, intracranial involvement carries major clinical significance due to its mass effect, potential to increase intracranial pressure, and risk of severe neurological deficits. In addition, clinical presentation is often nonspecific, and radiological resemblance to other cystic brain lesions may delay diagnosis and complicate management [2–4].

Pediatric patients account for a substantial proportion of intracranial cases (65%), and most lesions are solitary. Surgical excision remains the mainstay of treatment; however, intraoperative rupture and recurrence continue to pose significant challenges that may affect prognosis [2, 3].

In this context, we present the case of a 47-year-old woman with a hydatid cyst located within the pontomedullary region, a highly uncommon and surgically demanding location, who was successfully managed with controlled cyst aspiration followed by complete microsurgical excision, with marked postoperative clinical improvement. This case report was prepared in accordance with the CARE guidelines, and the completed CARE checklist is attached as online supplementary material.

Case presentation

A 47-year-old woman presented with progressive dysphagia and gradually worsening weakness involving both the upper and lower extremities over 4–6 weeks before admission. She denied headache, vomiting, fever, sensory symptoms, or constitutional complaints. She lived in a rural area and reported occasional exposure to dogs and livestock. Her past medical, surgical, allergic, and psychosocial history was otherwise unremarkable.

On admission, neurological examination revealed quadriparesis, with Medical Research Council (MRC) grade 2/5 power in the upper limbs and 3/5 in the lower limbs. Examination also demonstrated lower cranial nerve dysfunction, predominantly involving cranial nerves IX and X, manifested by dysphonia, a diminished gag reflex, and mild palatal asymmetry. Deep tendon reflexes were preserved, and plantar responses were bilaterally flexor. These findings localized the lesion to the brainstem and prompted urgent neuroimaging.

Non-contrast computed tomography (CT) of the brain demonstrated a well-defined hypodense cystic lesion in the pontomedullary region, without calcification. Brain magnetic resonance imaging (MRI) revealed a solitary, well-circumscribed, rounded intra-axial cystic lesion located in the pontomedullary junction. The lesion showed homogeneous cerebrospinal fluid–like signal characteristics, appearing hypointense on T1-weighted images, hyperintense on T2-weighted images, and suppressed on FLAIR sequences. It had a thin, smooth wall without internal septations, mural nodules, solid components, post-contrast enhancement, or surrounding edema. The lesion caused focal expansion of the pontine parenchyma with mild leftward mass effect toward the cerebellopontine angle (Fig. 1a, b, c, d, and e).

Fig. 1.

Pre-operative brain MRI. (a) Axial, (b) coronal, and (c) sagittal T1-weighted images show a hypointense well-circumscribed, rounded intra-axial cystic lesion located in the pontomedullary junction highlighted by a red circle. (d) Axial T2-weighted imaging shows marked homogeneous hyperintensity, and (e) axial FLAIR imaging shows near-complete signal suppression, consistent with CSF-like cyst content. The lesion is thin-walled, non-septated, and associated with focal expansion of the pontomedullary parenchyma, without appreciable surrounding edema

The radiological differential diagnosis included epidermoid, neurocysticercosis, neurenteric cysts, and arachnoid cysts. However, given the imaging characteristics in conjunction with the epidemiological background, a pontomedullary hydatid cyst was considered the most likely diagnosis.

A systemic work-up was performed to exclude extracranial involvement. Chest CT and abdominal ultrasonography showed no additional cystic lesions. Baseline laboratory investigations, including complete blood count, liver function tests, and peripheral eosinophil count (which was 0.13 × 10⁹/L; reference range 0.0–0.5 × 10⁹/L), were within normal limits.

A one-week course of preoperative albendazole at a dose of 400 mg twice daily was considered in order to reduce cyst viability and the risk of intraoperative spillage.

In view of the progressive neurological deficits and the eloquent brainstem location, surgical treatment was undertaken. Because of the deep-seated pontomedullary location and the limited operative corridor, standard Dowling–Orlando technique was considered unsuitable. The lesion was approached through a left lateral suboccipital craniotomy with the patient in the right lateral decubitus position under continuous neurophysiological monitoring. After microsurgical exposure of the operative corridor, the cyst was identified as a well-defined, tense, thin-walled lesion with a smooth pearly-white surface. Controlled puncture and aspiration of the cyst contents were therefore performed to achieve internal decompression and reduce wall tension. Following collapse of the cyst, the cyst wall was meticulously dissected under the operating microscope and removed completely. No uncontrolled rupture or intradural spillage occurred, and the operative field was carefully irrigated and inspected for any residual membrane. Complete microsurgical excision was achieved.

Histopathological examination demonstrated a laminated acellular cyst wall with an inner germinal layer, without identifiable protoscolices or significant associated inflammatory reaction, findings consistent with a hydatid cyst.

The postoperative course was uneventful. No new neurological deficits developed, and gradual neurological improvement was observed. Muscle strength improved to MRC grade 4+/5, with marked improvement in swallowing function, and dysphonia. Early postoperative CT confirmed complete excision of the lesion. The patient was monitored in the intensive care unit for 48 h, transferred thereafter to the neurosurgical ward, and discharged on postoperative day 7 in good general condition.

Albendazole therapy was initiated at a dose of 12 mg/kg/day in two divided doses for a planned duration of 4 months, with serial monitoring of liver function tests and complete blood counts.

Follow-up brain MRI obtained 2 weeks after surgery demonstrated complete excision of the pontomedullary hydatid cyst, with a small postoperative fluid-filled cavity at the resection site. No residual cystic lesion, residual mass effect, diffusion restriction, or hydrocephalus was identified (Fig. 2a, b, c, d, e, and f).

Fig. 2.

Two-week postoperative brain MRI. (a) Axial, (b) coronal, and (c) sagittal T1-weighted images show complete excision of the pontomedullary cystic lesion, with a small postoperative cavity at the resection site, highlighted by a green circle. (d) Axial T2-weighted imaging shows predominantly fluid signal within the cavity. (e) Diffusion-weighted imaging and (f) the corresponding apparent diffusion coefficient map shows no residual diffusion restriction. No residual mass effect, or hydrocephalus is seen

Discussion

Intracranial cystic echinococcosis comprises only a small proportion of intracranial mass lesions [3]. It is a rare manifestation of hydatid disease, with the majority of reported lesions located supratentorially and occurring predominantly in younger patients [2, 5]. By comparison, infratentorial involvement accounts for only (11.1%) of intracranial cases, mostly within the cerebellar hemispheres, and intra-brainstem localization remains extremely uncommon [2]. In this context, the present pontomedullary lesion in a middle-aged adult represents a distinctly unusual presentation within an already rare disease spectrum, with potentially serious implications for both bulbar and long-tract function.

Whereas most cerebral hydatid cysts present with manifestations of raised intracranial pressure, the clinical pattern in our patient was more closely related to lesion location within the pontomedullary region [5–7]. Progressive quadriparesis was consistent with long-tract involvement, while dysphagia and dysphonia reflected dysfunction of bulbar pathways and adjacent lower cranial nerve nuclei. This case therefore illustrates that, in CNS hydatid disease, clinical manifestations are determined primarily by lesion location rather than by parasite-specific features, and that brainstem lesions may present predominantly with focal neurological deficits before overt intracranial hypertension becomes prominent.

Preoperative recognition of intracranial hydatid cysts depends heavily on imaging, as clinical and laboratory findings are frequently nonspecific. In the present case, the combination of a well-circumscribed intra-axial cystic lesion with CSF-like signal intensity, a thin smooth wall, absence of calcifications, mural nodules, enhancement, or surrounding edema strongly favored a non-neoplastic parasitic cyst [2, 5]. The spherical intra-axial configuration of the lesion and FLAIR suppression helped argue against an epidermoid cyst [8, 9]. Also, given the endemic setting, neurocysticercosis (NCC) was a diagnostic consideration. However, it was effectively ruled out by the absence of characteristic imaging features, including an eccentric scolex, multiplicity, perilesional edema, ring enhancement, and restricted diffusion [10]. Arachnoid cysts were also considered less likely, as such lesions are typically extra-axial, sharply circumscribed, and follow CSF signal intensity on all MRI sequences [11]. Neurenteric cysts remain an important infratentorial differential consideration, especially near the brainstem; however, they are more often extra-axial and tend to show more variable, frequently protein-rich signal characteristics rather than the stereotypical CSF-like appearance observed in this case [12]. In endemic settings, the coexistence of typical imaging findings with supportive epidemiological exposure should lower the threshold for considering hydatid disease in the differential diagnosis of brainstem cystic lesions.

Given that intracranial echinococcosis may coexist with hydatid disease in other organs, preoperative systemic screening was performed in our patient using abdominal ultrasonography and chest CT. This approach is consistent with the standard imaging-based evaluation of hydatid disease and helped confirm that the lesion was apparently isolated, thereby refining operative planning [4, 13].

Surgery remains the cornerstone of treatment for intracranial hydatid cysts, with the ideal objective being complete removal without rupture in order to minimize recurrence, dissemination, and inflammatory or anaphylactic complications. The Dowling-Orlando technique is regarded as the classic operative approach for cerebral hydatid cysts and is based on generous surgical exposure, gentle hydrodissection with isotonic saline irrigation along the cyst-brain interface, and positioning maneuvers that facilitate controlled delivery of the cyst [4, 14, 15]. However, the operative principles established for superficial hemispheric cysts cannot always be directly applied to deep-seated brainstem lesions. In highly eloquent regions such as the pons or pontomedullary junction, the operative corridor is narrow and the margin for traction, hydrodissection, or decompression is limited. Surgical management should therefore be tailored to cyst depth, surgical accessibility, and proximity to critical neural structures [14, 16, 17]. In addition, comparable surgical challenges have been reported in peripontomedullary hydatid cysts, where the classic Dowling-Orlando technique may not be feasible due to restricted operative corridors [18]. In this respect, our case supports the view that careful microsurgical planning, rather than rigid adherence to a single standard technique, is essential for achieving safe resection in brainstem hydatid disease.

Adjunctive albendazole is frequently administered after surgery in cystic echinococcosis, particularly when there is concern for occult intraoperative spillage, residual disease, systemic involvement, or an increased risk of recurrence. Postoperative albendazole has been associated with favorable outcomes and is generally considered a risk-reduction measure rather than a substitute for definitive surgical treatment [4, 14, 19]. Because recurrence may be delayed even after apparently complete excision, postoperative surveillance should rely on serial neuroimaging, with the frequency and duration of follow-up tailored to the individual case and extended when there is concern for late relapse [20].

A narrative literature search was performed using PubMed and Google Scholar without date restrictions. The search strategy combined terms related to hydatid disease, intracranial involvement, and brainstem localization using the following Boolean query: (“hydatid cyst” OR echinococcosis OR echinococcal OR “Echinococcus granulosus” OR “cystic echinococcosis”) AND (brain OR cerebral OR intracranial OR “central nervous system” OR CNS) AND (brainstem OR “brain stem” OR pontine OR pons OR pontomedullary OR “pontomedullary junction” OR medulla OR “medulla oblongata” OR midbrain OR mesencephalon). Only intraparenchymal brainstem hydatid cyst case reports and case series were included. Other hydatid extra-brainstem or extracranial cysts were excluded. The search identified 10 previously published cases of intra-brainstem hydatid cysts [6, 7, 16, 17, 21–25] (Table 1).

Table 1.

Clinical, radiological, and management characteristics of previously reported intra-brainstem hydatid cyst cases

First author+Year/Study	Country	Age/Sex	Brainstem site	Extracranial disease	Main presentation	Management	Outcome	Follow-up
Abbassioun et al.1986 [7]	Iran	17/M	Pons	NR	Moderate right hemiparesis with inability to stand or walk;  CN V–X and XII palsies; cerebellar signs; and symptoms of raised intracranial pressure.	Prone-position surgery through the floor of the fourth ventricle; needle aspiration of the cyst followed by endocyst removal.	Postoperative death within 24 hours due to widespread hemorrhagic brainstem infarction.	24 h
Mascalchi et al.1991 [21]	Italy	60/M	Mid-pons	2 hepatic cysts	Recurrent right facial pain, paresthesia, and facial spasm; right-sided hearing loss; progressive left-leg numbness and gait disturbance; and symptoms of increased ICP.	Surgical excision of the pontine hydatid cyst together with the associated cerebellopontine angle acoustic neurinoma; surgical approach not reported.	NR	NR
Altinörs et al.1995 [22]	Turkey	4/F	Pons	None extracranial disease reported	Acute gait impairment with right partial dysphagia and dysarthria; right VII CN palsy.	Suboccipital craniotomy through the floor of the fourth ventricle; attempted Dowling delivery, followed by posterior myelotomy, cyst aspiration, and total capsule removal; hypertonic saline irrigation and postoperative mebendazole therapy.	Survived with transient CN V/VI palsies and bilateral dysmetria; regained independent ambulation with improving facial weakness and no recurrence reported.	3 months
*Boudawara et al.1999 [23]	Tunisia	NR	Brainstem (subsite NR)	NR	In both patients, Symptoms of increased ICP predominated.	In both patients, surgery consisted of cyst aspiration followed by membrane removal.	One patient died postoperatively; the surviving patient remained severely neurologically impaired, with no recurrence reported.	2 years (survivor)
Yilmazlar et al.1999 [24]	Turkey	3/M	Pons	2 cystic lesions in the thorax	Right hemiparesis with speech impairment and gait disturbance; left facial palsy; complex ocular motor palsies; and reduced gag reflex.	Sitting-position surgery through the floor of the fourth ventricle; gravity-assisted total excision using the Dowling technique.	Improvement in dysarthria and partial improvement in cranial nerve deficits; persistent nystagmus in the lateral fields of gaze; no recurrence reported.	Five weeks
Muthusubramanian et al.2009 [16]	India	40/F	Brainstem, left-sided (pons-predominant)	NR	Progressive right hemiparesis with headache, diplopia, and gait impairment; one-and-a-half syndrome with ipsilateral cerebellar signs.	Left retromastoid craniectomy via a middle cerebellar peduncle approach; controlled internal decompression by aspiration followed by total excision.	Progressive neurological recovery with only minimal residual cerebellar signs; no recurrence reported.	1 year
Alok et al.2020 [6]	Syria	5/F	Pons	Liver and kidney hydatid cysts	Right hemiparesis with right-sided  facial deviation, headache, and mild gait impairment; right esotropia and ptosis.	Suboccipital craniotomy with complete excision using Dowling’s technique; albendazole initiated 2 days preoperatively and continued postoperatively.	Neurological improvement with no recurrence reported.	4 months
Gader et al.2024 [17]	Tunisia	9/M	Pons	None extracranial disease reported	Hemiparesis with progressive gait impairment; CN V and VII palsies.	Left subtemporal approach; cyst puncture and aspiration followed by complete removal; postoperative albendazole therapy.	Neurological improvement with no recurrence reported.	2 years
Ghanem et al.2026 [25]	Syria	28/F	Medulla oblongata	None extracranial disease reported	Persistent headache with dysarthria, dysphagia, dysmetria, and gait impairment.	Modified PAIR-based microsurgical excision, followed by postoperative albendazole therapy.	Intraoperative cyst rupture and spillage occurred without anaphylaxis; delayed neurological improvement with no recurrence reported.	6 months

Abbreviations: NR not reported, CN cranial nerve, ICP intracranial pressure, CPA cerebellopontine angle, PAIR puncture, aspiration, injection, and re-aspiration

* Two patients were reported in aggregate; patient-level clinic-radiological details were incompletely available

Pontine involvement accounted for the majority of reported lesions, and one case of a medulla oblongata location. With respect to disease pattern, extracranial hydatid involvement was documented in 4 of 10 patients (40.0%), absent in 3 (30.0%), and not reported in 3 (30.0%); among classifiable cases, lesions associated with extracranial disease were slightly more frequent than isolated intra-brainstem lesions (57.1% vs. 42.9%). Geographically, the published cases were concentrated in endemic regions, with Mediterranean countries accounting for 8 of 10 cases (80.0%), and Tunisia contributed the largest proportion (30%). Among cases with available age data (n = 8), age ranged from 3 to 60 years (mean, 20.8 years; median, 13 years), and pediatric patients accounted for 62.5% of cases (5/8), a proportion specific to the published intra-brainstem cases identified in the present review. Across the published reports, the most frequent clinical pattern consisted of progressive long-tract dysfunction, gait impairment, and cranial nerve deficits, whereas features of raised intracranial pressure were reported less consistently. Surgical treatment was required in all reported patients, although the operative strategy differed according to lesion depth, surgical corridor, and relationship to eloquent brainstem structures. Outcomes were heterogeneous, ranging from postoperative death in some early reports to meaningful neurological recovery without recurrence in most of the later cases. The present case further supports that, despite this high-risk location, favorable recovery may be achieved with timely diagnosis, individualized surgical planning, and meticulous resection.

A limitation of this report is the relatively short radiological follow-up; therefore, continued long-term surveillance is planned to monitor for delayed recurrence. In addition, intraoperative photographs and histopathological images are not feasible due to infrastructural limitations at our institution, although the diagnosis was firmly established by conventional and documented histopathological examination. Another limitation is that Echinococcus‑specific serology was not performed due to its unavailability at our institution.

Conclusion

Intra-brainstem hydatid cysts are notably infrequent lesions that should nevertheless be considered in the differential diagnosis of well-circumscribed, non-enhancing cystic brainstem lesions, particularly in patients from endemic regions. This case highlights the pivotal role of integrating neuroimaging findings with epidemiological context to raise preoperative suspicion, as well as the importance of individualized microsurgical planning in eloquent locations where standard hydrodissection techniques may not be feasible. Despite the high-risk pontomedullary location, favorable neurological recovery can be achieved with timely diagnosis, carefully tailored surgical management, and postoperative adjunctive medical therapy and close follow-up.

Authors’ contributions

Ahmad Al Malla: Drafted the manuscript, compiled clinical data and imaging, reviewed successive versions, coordinated revisions, and approved the final version. Sama Saleh Alagol: Participated in writing the report, contributed to imaging selection and figure legends, participated in manuscript revisions, and approved the final version. All authors attest to the integrity of the work and agree to be accountable for all aspects of the manuscript.

Funding

No funding was received for this research.

Data availability

All data generated or analyzed during this study are included in this published article.

Declarations

Ethics approval and consent to participate

Ethical approval is not required for this study in accordance with local or national guidelines.

Consent for publication

Written informed consent was obtained directly from the patient for publication of the details of her medical case and any accompanying images.

Competing interests

The authors declare no competing interests.