Anti-GD1b-positive sensory ataxic Guillain-Barré syndrome with bulbar involvement and Bickerstaff brainstem encephalitis-like features in an adolescent: a case report

Article information

Clin Exp Pediatr. 2026;69(9):743-747

Publication date (electronic) : 2026 August 27

doi : https://doi.org/10.3345/cep.2026.00717

Hamza Reaz Aziz, MBBS¹, Kirsh Kumar, MBBS^,1, Nabiha Naveed, MBBS¹, Saira Awan, MBBS, FCPS²

¹Jinnah Sindh Medical University, Karachi, Pakistan

²Jinnah Postgraduate Medical Centre-JPMC, Karachi, Pakistan

Corresponding author: Kirsh Kumar. Jinnah Sindh Medical University – Sindh Medical College (SMC), Karachi, Pakistan Email: kirshbk792@gmail.com

Received 2026 March 26; Revised 2026 May 17; Accepted 2026 May 19.

Graphical abstract. Anti-GD1b-positive sensory ataxic Guillain-Barré syndrome with Bickerstaff brainstem encephalitis features. MRI, magnetic resonance imaging; IV, intravenous.

A 14-year-old child with no known comorbidities presented to the Emergency Department at Jinnah Postgraduate Medical Centre with a complaint of fever, abdominal pain, and generalized weakness for 15 days. The fever was initially low-grade (undocumented). Weakness began gradually in the lower limbs, progressed in an ascending pattern, and involved the upper limbs and trunk. The weakness progressed to the point that the patient became bedridden. There was no history of loss of consciousness, seizures, respiratory distress or need for ventilatory support. Seven to eight days before admission, the patient developed hypophonia, dysphagia, and an absent cough reflex. These findings were suggestive of bulbar involvement. The patient had no history of falls, trauma, surgery, vaccination, or recent travel. The patient was then referred to the Neurology ward at our hospital. Before admission, he had been prescribed only acetaminophen 500 mg twice daily for his fever and abdominal pain. No other treatment was given.

At the time of presentation, the patient was oriented to person and place but not to time and had a Glasgow Coma Scale of 14/15 (e4v4m6). He was mildly drowsy but obeyed commands, with no frank coma or severe encephalopathy. The vitals were as follows: blood pressure 110/70 mmHg, pulse 85 beats/min, respiratory rate 24 breaths/min, temperature 38.9°C, oxygen saturation 97% on room air, and single-breath count >20. The single-breath count is a bedside method for assessing respiratory muscle function. A count below 20 may suggest impending respiratory compromise. Cranial nerve examination revealed reduced palatal movement with hypophonia, dysarthria, and dysphagia. Extraocular movements were intact, and the pupils were reactive to light bilaterally. No ptosis or proptosis was observed. According to the Medical Research Council (MRC) scale, muscle power was 5/5 in both upper limbs and 4/5 in both lower limbs. The modified Erasmus Guillain-Barré syndrome (GBS) outcome score (mEGOS) predicts the ability of the patient to walk independently at the 4th week, 3 months, or 6 months. Lower scores are associated with a more favorable prognosis. His age was <40 years (0 point), absent diarrhea (0 point), and total MRC score was 54/60 (0 point), hence his mEGOS was 0 on both admission and week 1. With a high likelihood of regaining independence within the anticipated recovery period, this score indicates an excellent functional result. He had decreased muscle tone, absent reflexes, and a positive Babinski sign bilaterally. This contradiction between Babinski and areflexia may suggest a differential diagnosis involving both the central and peripheral nervous systems. Since the patient was bedridden at the time of initial presentation, heel-to-shin and gait could not be evaluated. It was later assessed as an ataxic gait. Finger-to-nose testing demonstrated dysmetria, and dysdiadochokinesia was present. No nystagmus was observed. Sensory examination showed intact light touch, pain, joint position, and proprioception. The rest of the systemic examination was unremarkable.

The preliminary examination included a complete blood count with a hemoglobin of 10.4 g/dL (normal range, 13–17 g/dL; mild anemia) and a leukocyte count of 6.2×10⁹/L (normal range, 4–11×10⁹/L). Serum electrolytes, coagulation profile, liver function tests, and renal function tests were all within normal limits. The erythrocyte sedimentation rate was markedly elevated at 50 mm/1st hr (normal range, <20 mm/1st hr) and C-reactive protein level was 81.76 mg/L (normal range, <5 mg/L). Magnetic resonance imaging (MRI) of the brain with contrast appeared unremarkable. Cerebrospinal fluid (CSF) examination revealed a normal cell count and a protein level of 33 mg/dL (normal range, 15–45 mg/dL). A repeat sample obtained 18 days later showed a slight increase in protein to 55 mg/dL. The chronological sequence of investigations and their findings is summarized in Table 1. The nerve conduction study (NCS) showed normal distal motor latencies, amplitudes, and conduction velocities. However, there was a decreased sensory nerve action potential (SNAP) amplitude with abnormal peak latencies. Overall, the findings were suggestive of sensory axonal loss (Table 2). Antibody profiles were sent to further differentiate immune-mediated pathologies, showing positive anti-GD1b and negative anti-GQ1b antibodies, as well as anti-GM1, anti-GD1a, and anti-GM2. The antibody panel was performed 17 days after admission.

Table 1.

Timeline for investigation

Table 2.

Nerve conduction study

Given this presentation, the patient was initially suspected of GBS or Bickerstaff brainstem encephalitis (BBE). Between these 2 differential diagnoses, BBE was considered more likely than GBS due to mild drowsiness. The patient was then administered intravenous (IV) methylprednisolone at a dose of 1 g for 5 days. The patient was observed for 5 days after IV steroid therapy and no clinical improvement was observed. Oral steroids were not recommended to the patient. The antibody panel was sent. During this period, the next treatment plan was plasmapheresis. Although the preferred therapy of GBS is IV immunoglobulins (IVIG) it was unavailable in our setup. Financial constraints limited the availability of IVIG, and plasmapheresis was therefore performed. Thus, the risks and benefits of treatment were explained to the patient, and 5 plasmapheresis sessions were performed over 15 days. Plasmapheresis resulted in significant clinical improvement; his consciousness improved along with his disability. On the 29th day after the admission, the Hughes disability score was 3, and the patient was able to walk with support. General nursing care was provided, including bowel and bladder management, pressure sore prevention, deep vein thrombosis prophylaxis, and physiotherapy.

The patient was then asked to have regular weekly follow-ups, but this was not possible because the patient lived in a remote rural area, and the family had a very low socioeconomic background, making regular follow-ups very difficult due to financial constraints. He was then requested to have a 3-month follow-up. At his first follow-up session, the patient was healthy, with no recurrent infections, injuries, or endemic infections. Complete general and neurological examination had been performed on the patient, and he was still found to be ataxic. The Hughes disability score is the most commonly used scale to measure the severity of GBS. According to the patient's evaluation, at the time of presentation, his Hughes disability score was 4, and after plasmapheresis, it increased to 3 within a month. On a 3-month followup, it was graded 2 on the basis of his ability to walk independently but not run.

The patient was initially suspected of GBS, given the signs of peripheral weakness and areflexia. GBS is a postinfection, immune-mediated neuropathy causing symptoms such as weakness, tingling, and numbness that can progress to flaccid paralysis [1]. In our patient, ascending weakness, areflexia, bulbar involvement, later mildly elevated CSF protein, and NCS evidence of sensory axonal involvement supported a diagnosis within the GBS spectrum. The patient was later examined for ataxia, which gave a false impression of GBS and pointed towards a variant of GBS known as Miller Fisher syndrome (MFS). It is a rare variant of GBS characterized by the classic triad of ataxia, areflexia, and ophthalmoplegia [2]. Although the patient was not suffering from ophthalmoplegia, a diagnosis can still be considered if any two of the following features are present [3]. The patient had been suffering from low-grade fever (undocumented) without any respiratory involvement or gastrointestinal symptoms. The disease spectrum follows a postinfection immunemediated neuropathy, usually caused by Campylobacter jejuni [4]. However, no serology report other than the blood culture was available, which showed Staphylococcus species but not aureus.

The subsequent impairment in the level of consciousness (mild drowsiness) was indicative of BBE. It is a clinical triad of progressive ophthalmoplegia, ataxia, and impaired consciousness [5]. MRI can detect abnormalities, but it was within normal limits in our patient. Due to nonresolving drowsiness and confused speech for at least 5 days, the patient was prescribed to undergo IV methylprednisolone therapy rather than plasmapheresis due to suspected BBE involvement. A pediatric literature review of case series on BBE and GBS reported that 46% of cases showed positive anti-GQ1b antibodies. NCS studies were normal in 64% of cases, whereas MRI brainstem abnormalities were observed in only a minority (up to 25%), underscoring the diagnostic challenge when central and peripheral signs coexist [6]. Although serum anti-GQ1b IgG is frequently detected, its absence does not exclude the diagnosis [7]. Antiganglioside antibody profiles were sent for further evaluation, but their patterns do not help stratify the clinical phenotypes and are not definitively diagnostic. The antibody panel for our patient showed positive anti-GD1b and negative anti-GQ1b antibodies, as well as anti-GM1, anti-GD1a, and anti-GM2. The positive anti-GD1b has been repeatedly seen in patients with sensory-predominant/ataxic GBS and sensory neuronopathies; cases with prominent sensory ataxia and reduced SNAP amplitudes have correlated with GD1b positivity, as in the case of our patient, which supports an immune-mediated sensory/ataxic neuropathy [7]. It was shown that anti-GD1b is more associated with sensory ataxia whereas anti-GQ1b and anti-GT1a are linked with ophthalmoplegia [8].

Albuminocytological dissociation is defined as an increased protein level (>0.45 g/L) in the absence of an elevated white cell count (<50 cells/μL) [9]. The initial CSF protein sample was normal at 33 mg/dL, while the repeat CSF after 20 days showed a mild rise to 55 mg/dL. This suggests the mild albuminocytological dissociation. The patient’s NCS report has shown sensory axonal involvement. Although bedside sensory examination was intact, clinical sensory modalities may be preserved despite electrophysiological sensory nerve involvement, especially in early or mild sensory neuropathy.

One atypical feature in our patient was an upgoing plantar reflex, as reported in a cohort study that found that approximately 40% of patients with BBE/anti-GQ1b overlap syndrome present with a positive upgoing plantar reflex [5]. Acute ataxic variant of GBS, BBE, and acute ophthalmoparesis, are collectively known as the anti-GQ1b syndrome. This anti-GQ1b antibody spectrum is best viewed as a clinical and immunopathological continuum rather than strictly separated entities. Anti-GQ1b antibodies are classically found in patients with MFS/BBE who present with ophthalmoplegia, ataxia, and altered level of consciousness [7,10]. Our patient was negative for anti-GQ1b and did not develop ophthalmoplegia, pointing towards a negative diagnosis for this syndrome.

Although the standard therapy of GBS includes IVIG but its unavailability and financial constraint led to the administration of plasma exchange for 5 consecutive sessions. A few days after therapy, the patient's speech and disability status began to improve significantly.

This case highlights the anti-GD1b sensory ataxic GBS with bulbar involvements and BBE like features. The main takeaway message is to consider anti-GD1b-associated sensory ataxic GBS/BBE overlap in adolescents with acute ataxia, bulbar signs, areflexia, and albuminocytological dissociation.