The Role of Prenatal Neurosonography in Identification of Tubulinopathy—Narrative Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

1. While the manuscript provides a comprehensive overview of prenatal neurosonographic features of tubulinopathies, it does not address the epidemiological aspects of these disorders, such as incidence, prevalence, or their relative contribution to neurodevelopmental disease. Inclusion of epidemiological data would be important to contextualize the clinical relevance of tubulinopathies, clarify the scale of the problem, and allow readers to better appreciate how frequently such conditions may be encountered in routine clinical practice in comparison with other neurodevelopmental disorders.

 

 

2. Comment in regard to manuscript text lines 96-99: The statement that extracerebral manifestations are merely secondary to central nervous system involvement appears overly restrictive. Available evidence suggests that extracerebral manifestations in tubulinopathies are not simply secondary phenomena but may represent primary components of a syndromic disease spectrum, as illustrated by cases with fetal akinesia deformation sequence, arthrogryposis, and peripheral neuromuscular involvement. Here are references of interest:

Weber M, Jaber D, Encha-Razavi F, Julien E, Grevoul-Fesquet J, Steffann J, Melki J, Martinovic J. Broadening the phenotypic spectrum of TUBA1A tubulinopathy to syndromic arthrogryposis multiplex congenita. Am J Med Genet A. 2022 Aug;188(8):2331-2338.

Li D, Shen KM, Zackai EH, Bhoj EJ. Clinical variability of TUBB-associated disorders: Diagnosis through reanalysis. Am J Med Genet A. 2020 Dec;182(12):3035-3039. 

Laquerriere A, Gonzales M, Saillour Y, Cavallin M, Joyē N, Quēlin C, Bidat L, Dommergues M, Plessis G, Encha-Razavi F, Chelly J, Bahi-Buisson N, Poirier K. De novo TUBB2B mutation causes fetal akinesia deformation sequence with microlissencephaly: An unusual presentation of tubulinopathy. Eur J Med Genet. 2016 Apr;59(4):249-56.

 

3. Comment in regard to manuscript text lines 245-247: Counselling should address potential intrafamilial differences in neurological and developmental outcomes. For example, pathogenic variants in genes such as TUBB3 can show striking intrafamilial variability, with carriers in the same family exhibiting normal cognition, mild motor impairment, or more severe neurological phenotypes, underscoring challenges in prognosis and genetic counselling. Here is the reference of interest:

Bouazzaoui A, Quélin C, Rozel C, Carré W, Dubourg C, Odent S, Rollier P. Expanding the TUBB3-Related Phenotypic Landscape: Fetal Diagnosis of Novel TUBB3 Variant Linked With Phenotypic Variability Within a Single Family. Prenat Diagn. 2025 Jan;45(1):134-137.

Author Response

Ad. Comment 1.

Thank you for this valuable suggestion. We agree that including epidemiological context strengthens the clinical relevance of the review. We have now added a brief paragraph at the end of the Introduction section, summarizing the rarity of tubulinopathies and their relative frequency in cohorts with malformations of cortical development. The added text reads:

Tubulinopathies are rare neurodevelopmental disorders, with an estimated prevalence of less than 1 in 1,000,000 for specific subtypes such as tubulinopathy-associated dysgyria (Orphanet: 467166) [7]. However, in selected cohorts of patients with complex malformations of cortical development (MCD), including lissencephaly, polymicrogyria, or microlissencephaly, pathogenic variants in tubulin genes account for a substantial proportion, ranging from approximately 10–40% depending on the series and selection criteria [10]. This highlights their relative importance among genetic causes of fetal brain malformations encountered in prenatal practice, particularly when ventriculomegaly, callosal anomalies, or cerebellar hypoplasia are identified on routine ultrasound, warranting targeted genetic evaluation.

 

Ad. Comment 2.

We thank the reviewer for highlighting this important nuance and for providing relevant references. We agree that the original statement was overly restrictive and did not fully capture the broader phenotypic spectrum of tubulinopathies, particularly in severe prenatal presentations. We have revised the sentence in the Pathophysiology section to acknowledge that while many extracerebral features are considered secondary to CNS involvement, some (e.g., arthrogryposis multiplex congenita and fetal akinesia deformation sequence) may represent primary components of the disease spectrum. The revised text now reads:

Extracerebral manifestations, such as ocular anomalies (strabismus, ptosis), sensorimotor polyneuropathy, pseudobulbar palsy with facial diplegia, and in rarer cases, more extensive syndromic features including arthrogryposis multiplex congenita or fetal akinesia deformation sequence, have been described. While many of these are considered secondary to central nervous system involvement (e.g., due to disrupted axonal guidance or motor neuron function), emerging evidence suggests that some extracerebral features, particularly severe neuromuscular involvement leading to fetal akinesia or arthrogryposis, may represent primary components of the tubulinopathy spectrum rather than purely secondary phenomena [32-34]

 

Ad. Comment 3.

Thank you for this helpful comment and for suggesting the recent reference. We agree that intrafamilial variability (especially in TUBB3 cases) is important for counseling and should be mentioned. We have added this point to the Implications for Prenatal Counseling section. The updated text now reads:

Counseling should address phenotypic variability, reproductive options, and potential for atypical seizures like infantile spasms[26]. Particular attention should be paid to potential intrafamilial differences in neurological and developmental outcomes, especially in inherited cases involving genes such as TUBB3. Pathogenic variants in TUBB3 can exhibit striking intrafamilial variability, with carriers in the same family displaying a wide range of phenotypes—from normal cognition and mild motor impairment to more severe neurological deficits—highlighting challenges in accurate prognosis and genetic counseling [35].

Reviewer 2 Report

Comments and Suggestions for Authors

This is a very timely and clinically relevant narrative review addressing an important and challenging topic in prenatal medicine. The manuscript successfully highlights the growing role of dedicated neurosonography in raising suspicion for tubulinopathies and provides practical tools such as structured criteria tables and a diagnostic algorithm. The focus on recent literature (2019–2025) is appropriate, and the integration of ultrasound, MRI, and genetic findings is a clear strength. The paper has the potential to become a useful reference for obstetricians and fetal medicine specialists.

That said, several important issues need to be addressed before publication.

First, although the manuscript is described as a narrative review, the abstract states that the literature was “systematically synthesized.” However, no description of the search strategy, databases, inclusion criteria, or study selection process is provided. Even for a narrative review, readers need basic methodological transparency. The authors should briefly explain how the literature was selected, which databases were searched, what time frame was applied, and how studies were chosen. Without this, the review lacks reproducibility and clarity.

Second, the manuscript occasionally overstates the diagnostic power of ultrasound. Statements suggesting that routine anomaly scans can identify suggestive signs “in the majority of cases” or that ultrasound findings alone can reliably raise suspicion should be moderated. Prenatal neurosonography is highly operator-dependent, and mild forms of tubulinopathy are subtle and frequently missed. The authors should acknowledge interobserver variability, gestational age limitations, and the essential role of fetal MRI and genetic testing in confirmation. A more balanced tone would strengthen the scientific credibility of the paper.

Third, the counseling section would benefit from more neutral and carefully phrased language. While the poor prognosis of many tubulinopathies is well established, wording such as “no independent life” may sound directive rather than informative. Counseling should be presented as empathetic, individualized, and non-directive, recognizing phenotypic variability and differences in legal and cultural contexts. A slight refinement in tone would make this section more ethically balanced.

The discussion of inheritance patterns also needs clarification. The manuscript contrasts >95% de novo mutations in severe forms with approximately 53% inherited cases in mild forms. This difference should be explained more clearly whether it reflects biological differences, detection bias, increased identification of mosaic parents, or characteristics of selected cohorts. As currently written, the contrast may confuse readers.

The differential diagnosis section is useful but somewhat simplified. Additional clarification on how to distinguish dysgyria from polymicrogyria on imaging, and when to prioritize testing for dystroglycanopathies or mTOR-related disorders, would make this section stronger. A slightly deeper discussion would enhance its clinical utility.

Finally, the figures would benefit from clearer labeling and contextual information. It would be helpful to specify gestational age and whether the cases shown were genetically confirmed tubulinopathies. Adding arrows or highlighting key structures would improve the educational value of the images.

In summary, this is a strong and clinically valuable review with practical applicability, but it requires methodological clarification, moderation of certain claims, refinement of tone in the counseling section, and clearer discussion of inheritance patterns. With these revisions, the manuscript would make a meaningful contribution to the field of prenatal neuroimaging.

     

Author Response

Ad. Comment 1.

Thank you for this valuable comment. We agree that basic methodological transparency is important even for a narrative review. We have removed the word “systematically” from the abstract to better reflect the narrative character of the work.

We have also added a short paragraph describing the literature search process at the end of the Introduction section. It includes the databases used (PubMed/MEDLINE and Google Scholar), keywords, time frame (2019–2025), and selection criteria. This provides readers with clear information on how the literature was identified and chosen.

 

Ad. Comment 2.

Thank you for this important observation. We agree that the original wording may have overstated the diagnostic capability of routine ultrasound, particularly for mild tubulinopathies, which are often subtle and operator-dependent. We have moderated the tone throughout the manuscript by:

• Revising statements in the Introduction and Conclusion to emphasize that ultrasound can raise suspicion in many cases but requires dedicated expert neurosonography, and that mild forms are challenging to detect on routine scans.
• Adding a paragraph acknowledging limitations of prenatal ultrasound, including operator dependence, interobserver variability, gestational age effects (better visualization after 28 weeks), and the complementary role of fetal MRI and genetic testing for confirmation (added at the end of the Prenatal Neurosonographic Signs section, subsection 3.1).

These changes provide a more balanced perspective and highlight the need for multidisciplinary confirmation, improving the scientific credibility of the review.

 

Ad. Comment 3.

Thank you for this thoughtful comment. We fully agree that prenatal counseling language should be neutral, empathetic, non-directive, and sensitive to variability and contextual factors. We have revised the Implications for Prenatal Counseling section to soften the tone and avoid potentially directive phrasing. Specifically, we replaced the sentence about “no independent life” and related statements with more balanced words that acknowledge the typically severe prognosis while emphasizing phenotypic variability, individual differences, and the need for empathetic, individualized, non-directive counseling that respects legal, cultural, and personal contexts. The revised text now reads:

Parents should be informed about the typically severe neurodevelopmental prognosis in most cases of tubulinopathy, which often includes profound intellectual disability, drug-resistant epilepsy, significant motor impairment, and a high likelihood of lifelong support needs. However, the exact outcome can vary, depending on the specific genetic variant, degree of brain malformation, and individual factors. Given the phenotypic variability (including milder presentations in some inherited cases), counseling should emphasize the range of possible outcomes and the importance of multidisciplinary approach (geneticists, fetal medicine specialists, psychologists) to support parents throughout the process. Counseling must remain empathetic, individualized, non-directive, and sensitive to legal, cultural, and personal contexts, allowing parents to make fully informed decisions based on their values and circumstances.

 

Ad. Comment 4.

Thank you for this excellent point. We agree that the contrast in inheritance patterns between severe and mild forms requires clearer explanation to avoid confusion. We have revised the relevant sentence in the Gene-Specific Associations subsection to distinctly address the biological and methodological reasons for this difference. The updated text now reads:

Inheritance was seen in 18 out of 34 cases (53%) in the group of mild tubulinopathies, usually passed on from parents with mild symptoms or mosaic changes [14]. In severe forms, mutations are almost always de novo (>95%), because these changes are much more harmful and parents with them rarely have children. The higher number of inherited cases in milder forms comes from two main reasons: some mutations are less harmful, so they can be passed to the child and prenatal studies often find these milder, survivable changes [15,29].

 

Ad. Comment 5.

Thank you for this helpful suggestion. We agree that adding more detail on imaging differentiation and clinical prioritization improves the practical value of the differential diagnosis section. We have expanded this section with a clearer explanation of how dysgyria appears on fetal MRI/neurosonography compared to polymicrogyria, and when to prioritize testing for dystroglycanopathies (e.g., severe cerebellar/pontine changes + eye/muscle signs) or mTOR disorders (e.g., tubers + multiorgan involvement).

The added text now reads:

MRI helps differentiate dysgyria from true polymicrogyria [21]. Dysgyria in tubulinopathies typically appears on fetal MRI or dedicated neurosonography as irregular, shallow, obliquely oriented sulci with variable depths and poor operculization, often asymmetric and without the classic 'cobblestone' or excessively thick cortex seen in polymicrogyria. In contrast, true polymicrogyria shows multiple small, tightly packed gyri with an irregular cortical-white matter junction, frequently bilateral and perisylvian, and may be associated with schizencephaly in some cases. Distinguishing these patterns requires high-resolution imaging, preferably fetal MRI after 28 weeks, as ultrasound alone may not provide sufficient detail for reliable differentiation.

When ventriculomegaly is accompanied by severe cerebellar hypoplasia, pontine thinning, or eye/muscle abnormalities, dystroglycanopathies (e.g., Walker-Warburg syndrome) should be prioritized in the differential diagnosis and tested for early (via targeted gene panel or exome). Similarly, if cortical malformations are accompanied by tubers, subependymal nodules, or cardiac/renal findings, this should lead to genetic testing towards mTOR-related disorders (e.g., tuberous sclerosis). In the absence of these extracerebral or syndromic features, tubulin gene sequencing remains the most appropriate next step.

 

Ad. Comment 6.

Thank you for this practical suggestion. We agree that enhancing the figures with clearer captions and visual annotations will increase their educational value. We have revised all figure captions (Figures 1–5) to include:

• approximate gestational age (GA) at imaging,
• information on whether the case was genetically confirmed,
• description of added arrows for key structures.

We have also added arrows directly to the figures where appropriate. The updated captions now provide better context and make the images more self-explanatory for readers.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I believe the revised manuscript is suitable for publication in its current form