Poland–Möbius syndrome in infancy: Clinical and imaging findings – A case report

INTRODUCTION

Möbius (Moebius) and Poland’s syndromes are two rare congenital syndromes characterized by non-progressive bilateral (and often asymmetric) dysfunction of the 6^th and 7^th cranial nerves and hypoplasia of the pectoral muscles associated with chest wall and upper-limb anomalies, respectively.^[1] The earliest sign is the inability of the newborn to suckle, mask-like facies with absent facial expressions, especially when crying, inability to close eyes completely or move them laterally and drooling. Inability to blink may lead to corneal abrasions seen in Mobius syndrome. Paralysis may be unilateral or bilateral. The spectrum of abnormalities seen in Poland syndrome: Aplasia or hypoplasia of pectoralis major (most common), pectoralis minor, ipsilateral 2^nd–5^th ribs, ipsilateral breast, and upper-limb abnormalities include small hand and brachydactyly, syndactyly, and single transverse palmar crease of the affected extremity.^[2]

The co-occurrence of both syndromes – Poland–Möbius syndrome – is uncommon but recognized. Poland–Möbius syndrome is thought to result from intrauterine vascular disruption around the 6^th week, affecting the subclavian and/or vertebral arteries leading to brainstem, cranial nerves malformation, and the ipsilateral limb/chest structures;^[1,3] while most cases are sporadic, genetic factors including Plexin D1 (PLXND1) and Rev3-like protein (REV3L) mutations and chromosomal abnormalities have been reported.^[4] Awareness of this association is crucial for early diagnosis and management.

This case is distinctive for its early infancy presentation and detailed cranial nerve assessment using 3D fast imaging employing steady-state acquisition (FIESTA) magnetic resonance imaging (MRI) sequences enabled detailed visualization of the facial (VII) and abducens (VI) nerve nuclei and their cisternal segments, allowing comprehensive cranial nerve assessment that confirmed isolated VI–VII palsy without involvement of other lower cranial nerves.^[5]

CASE REPORT

We present a case of a 5-month-old male infant with left-sided facial palsy at birth. He was delivered at 38 weeks of gestation through cesarean section, with a normal birth weight and height. There was no maternal history of diabetes, hypertension, or exposure to teratogenic substances during pregnancy. The infant was the second child of nonconsanguineous parents, with no significant family history of congenital anomalies. The infant presented with an inability to close the left eye, left esotropia, and mild difficulty with breastfeeding, without any significant respiratory compromise. Facial asymmetry with mouth deviation to the right was evident. Examination of the right upper limb revealed clinodactyly of the little finger and syndactyly and brachydactyly of the 2^nd and 3^rd fingers. Palpation and imaging indicated hypoplasia of the right pectoralis major muscle, while the left side appeared normal [Figure 1].

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Figure 1:

(a) Clinical image shows f acial asymmetry with left eye incomplete closure (pink arrow) and mouth deviation to the right, (b) Right hand with clinodactyly of little finger, syndactyly, and brachydactyly of 2^nd and 3^rd finger (pink arrow), (c) Hyperlucency of the right hemithorax (blue arrow) suggestive of pectoral muscle absence, (d) Ultrasound image shows hypoplasia of right pectoralis major (pink arrow) and left pectoralis major appears normal (blue arrow), (e) Radiograph of right-hand anteroposterior view shows clinodactyly of little finger.

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The 3D FIESTA sequence, a type of T2-weighted sequence, produces bright signals for fluids such as cerebrospinal fluid and dark signals for nerves and vessels. The technique is a key part of evaluating pathologies involving cranial nerves, especially those exiting the brainstem and traversing the subarachnoid space, including the cerebellopontine angle cistern.

MRI was performed on a 3.0 T scanner (GE SIGNA Architect) using T1-weighted, T2-weighted, and 3D FIESTA sequences in axial, coronal, and sagittal planes. Sequence parameters included repetition time of 6.5 ms, echo time of 2.7 ms, and a slice thickness of 0.6 mm for the 3D FIESTA axial sequence. confirming absence of the left abducens (VI) and facial (VII) nerves with flattening of the floor of the fourth ventricle and loss of the left facial colliculus, while the contralateral nerves appeared normal [Figure 2].

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Figure 2:

Magnetic resonance imaging (MRI) image. (a) Axial 3D fast imaging employing steady-state acquisition (FIESTA) demonstrates flattening of the floor of the fourth ventricle and absence of the left facial colliculus (yellow arrow), suggestive of facial nerve nucleus aplasia on the left side, (b) image at the level of the cerebellopontine angle cisterns. The left facial nerve and left abducens nerve are not visualized. The right facial nerve (green arrow), bilateral vestibulocochlear nerves (yellow arrows), and right abducens nerve (blue arrows) are clearly identified. The cisternal segments of the left CN VI and VII are absent. (c) Parasagittal 3D FIESTA MRIs through the internal auditory canals (IACs), normal right IAC showing typical anatomy with facial nerve (anterosuperior) (yellow arrow), cochlear nerve (anteroinferior), and vestibular n erves (posteriorly). (d) Parasagittal 3D FIESTA MRIs through the IACs. Left IAC shows absent facial nerve in the anterosuperior quadrant (yellow arrow); cochlear and vestibular nerves are visualized in their respective positions. Findings indicate aplasia of the canalicular segment of the left facial nerve.

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DISCUSSION

The presented case highlights the rare co-occurrence of Poland and Möbius syndromes. The findings underscore the role of vascular disruption during early embryogenesis, particularly the subclavian artery supply disruption sequence, which can simultaneously impair pectoral muscle formation and brainstem development.^[1,3,4]

Genetic studies have identified PLXND1 and REV3L mutations as possible contributors to this combined phenotype (Glass et al., 2022).^[4] Approximately 20% of reported Möbius cases show associated Poland features, though this estimate varies due to small sample sizes (McClure et al., 2017).^[6] Poland syndrome may initially be suspected based on physical examination or incidentally noted on imaging, such as a hyperlucent hemithorax on chest radiographs, especially in the absence of cardiopulmonary symptoms. Möbius syndrome may be detected early due to facial weakness and feeding difficulties. MRI for evaluating cranial nerve abnormalities and specific protocols should include high-resolution heavily T2-weighted sequences, thin-slice imaging of the brainstem, and internal auditory canal evaluation with sagittal and axial reconstructions.

DIFFERENTIAL DIAGNOSIS

The differential diagnosis is presented in Table 1.

CONCLUSION

Poland–Möbius syndrome is a rare but important association involving musculoskeletal and cranial nerve anomalies. Early recognition through detailed clinical and imaging evaluation is crucial for diagnosis, prognosis, and multidisciplinary management. Radiologists should recommend a combined cranial nerve and chest wall assessment in cases of unilateral facial or thoracic anomalies.

TEACHING POINTS

1. Combined Poland–Möbius syndrome should be suspected in infants with unilateral chest wall hypoplasia and facial weakness.

2. High-resolution 3D FIESTA MRI enables direct visualization of cranial nerve aplasia.

3. Early radiological recognition guides multidisciplinary management and prognostication.

MCQs

1. Which feature combination defines Poland–Möbius syndrome?

   1. Pectoralis muscle hypertrophy with ocular palsy

   2. Pectoralis muscle hypoplasia with VI and VII cranial nerve palsy

   3. Latissimus dorsi absence with glossopharyngeal palsy

   4. Facial palsy with cardiac defect

   Answer Key: b

2. On MRI brain, the most typical finding in the Möbius component is:

   1. Dilated lateral ventricles

   2. Absence or hypoplasia of the abducens and facial nucle with flattening of the 4^th ventricle floor

   3. Hypoplastic cerebellar vermis

   4. Basal ganglia calcifications

   Answer Key: b

3. The most commonly absent muscle in Poland syndrome is:

   1. Latissimus dorsi

   2. Pectoralis major (sternocostal head)

   3. Trapezius

   4. Serratus anterior

   Answer Key: b