Petrous Bone Research Articles

Anteromedial Petrous (Gardner's) Triangle: Surgical Anatomy and Relevance for Endoscopic Endonasal Approach to the Petrous Apex and Petroclival Region.

Triangular corridors have been used as reliable surgical entry points for open transcranial approaches to the petrous apex (PA) and petroclival region (PCR). The endoscopic endonasal approaches have grown rapidly in the last decade, and the indications have advanced. The knowledge of accurate and reliable anatomic landmarks through endoscopic endonasal route is essential and remain to be established. The purpose of this study was to describe the feasibility and surgical exposure of the anteromedial petrous (Gardner's) triangle as a novel corridor to the PA and PCR. Five anatomic specimens were dissected. The PA and PCR were accessed through endoscopic endonasal approaches and contralateral transmaxillary approach. The limits of the anteromedial petrous (Gardner's) triangle were identified and dissected and associated measurements performed. The dissection was divided into 6 steps. The limits of the anteromedial petrous (Gardner's) triangle were identified and defined by the paraclival internal carotid artery anterolaterally, the abducens nerve posteromedially, and the petroclival synchondrosis inferiorly. Three lines were established following the limits of the triangle. The mean distance of the anterolateral limit was 10.03 mm (SD = 0.94), of the posteromedial limit was 20.06 mm (SD = 2.90), and of the inferior limit was 17.99 mm (SD = 2.99). The mean area was 87.56 mm 2 (SD = 20.06). The 3 anatomic landmarks with a critical role to safely define the triangle were the pterygosphenoidal fissure, the petrosal process of the sphenoid bone, and the petroclival synchondrosis. The anteromedial (Gardner's) triangle is a well-defined bone corridor which provides access to the entire petrous bone and petroclival junction through endoscopic endonasal route. Regardless of the anatomic variations or tumor location, the landmarks of the abducens nerve, paraclival internal carotid artery, and petroclival synchondrosis are key for understanding lateral access to tumors extending from the clivus.

Petroclival Clinoidal Folds and Arachnoidal Membranes of the Anteromedial Incisural Space: Clinical Anatomy for Neuro Critical Care.

A systematic and narrative literature review was performed, focusing attention on the anatomy of the area located at the junction of the sphenoid and the basal portion of the temporal bone (petrous bone, petrous apex, upper petro-clival region) encircled by the free edge of the tentorium, the insertion of the tentorium itself to the petrous apex and the anterior and posterior clinoid processes that give rise to three distinct dural folds or ligaments: the anterior petroclinoid ligament, the posterior petroclinoid ligament and the interclinoid ligament. These dural folds constitute the posterior portion of the roof of the cavernous sinus denominated "the oculomotor triangle". The main purpose of this review study was to describe this anatomical region, particularly in the light of the relationships between the anterior margin of the free edge of the tentorium and the above-mentioned components of the sphenoid and petrous bone.

Performance comparison of four qPCR and three autosomal STR commercial kits from degraded skeletal remains

This research evaluates the current DNA quantification (Quantifiler™ Trio, PowerQuant®, Investigator® Quantiplex® Pro and InnoQuant® HY Fast) and autosomal STRs amplification kits (GlobalFiler™, PowerPlex® Fusion 6 C, Investigator® 24Plex QS) using 62 degraded skeletal remains from armed conflicts (petrous bone, femur, tibia, and tooth) with several parameters (autosomal small, large, and male target, degradation index, probability of degradation, number of alleles above analytical threshold, number of alleles above stochastic threshold, RFU, peak height ratio, number of reportable loci). The best qPCR/autosomal STRs amplification tandem was determined by comparing quantification results by a DNA quantity estimation based on sample average RFU. InnoQuant® HY Fast was the most sensitive kit, and no significative differences were observed among amplification kits; however, Investigator® 24 Plex QS was found to be the most sensitive in our samples. That is why InnoQuant™ and Investigator® 24Plex QS were determined to be the best tandem.

A proposed classification system for presigmoid approaches: a scoping review.

The "presigmoid corridor" covers a spectrum of approaches using the petrous temporal bone either as a target in treating intracanalicular lesions or as a route to access the internal auditory canal (IAC), jugular foramen, or brainstem. Complex presigmoid approaches have been continuously developed and refined over the years, leading to great heterogeneity in their definitions and descriptions. Owing to the common use of the presigmoid corridor in lateral skull base surgery, a simple anatomy-based and self-explanatory classification is needed to delineate the operative perspective of the different variants of the presigmoid route. Herein, the authors conducted a scoping review of the literature with the aim of proposing a classification system for presigmoid approaches. The PubMed, EMBASE, Scopus, and Web of Science databases were searched from inception to December 9, 2022, following the PRISMA Extension for Scoping Reviews guidelines to include clinical studies reporting the use of "stand-alone" presigmoid approaches. Findings were summarized based on the anatomical corridor, trajectory, and target lesions to classify the different variants of the presigmoid approach. Ninety-nine clinical studies were included for analysis, and the most common target lesions were vestibular schwannomas (60/99, 60.6%) and petroclival meningiomas (12/99, 12.1%). All approaches had a common entry pathway (i.e., mastoidectomy) but were differentiated into two main categories based on their relationship to the labyrinth: translabyrinthine or anterior corridor (80/99, 80.8%) and retrolabyrinthine or posterior corridor (20/99, 20.2%). The anterior corridor comprised 5 variations based on the extent of bone resection: 1) partial translabyrinthine (5/99, 5.1%), 2) transcrusal (2/99, 2.0%), 3) translabyrinthine proper (61/99, 61.6%), 4) transotic (5/99, 5.1%), and 5) transcochlear (17/99, 17.2%). The posterior corridor consisted of 4 variations based on the target area and trajectory in relation to the IAC: 6) retrolabyrinthine inframeatal (6/99, 6.1%), 7) retrolabyrinthine transmeatal (19/99, 19.2%), 8) retrolabyrinthine suprameatal (1/99, 1.0%), and 9) retrolabyrinthine trans-Trautman's triangle (2/99, 2.0%). Presigmoid approaches are becoming increasingly complex with the expansion of minimally invasive techniques. Descriptions of these approaches using the existing nomenclature can be imprecise or confusing. Therefore, the authors propose a comprehensive classification based on the operative anatomy that unequivocally describes presigmoid approaches simply, precisely, and efficiently.

The prevalence of elongated styloid process in the population of Barcelona: a cross-sectional study & review of literature

BackgroundStyloid process (SP) is a cylindrical bony projection that originates from the inferior part of the petrous temporal bone just anteriorly to the stylomastoid foramen. Several nerves, muscles, and ligaments are related closely to the (SP). It is considered elongated when the measurement exceeds 30 mm. The overall prevalence of the styloid process is between 3.3% to 84.4%. The elongation of the styloid process (ESP) is associated with the manifestation of Eagle’s Syndrome (ES) which is characterized by various types of pain in the head and neck region such as headache, tinnitus, otalgia, and trigeminal neuralgia. Eagle’s syndrome occurs in 4–10.3% of individuals with an elongated styloid process (ESP). The objective of the study is to determine the prevalence of (ESP) in the patients who were treated in the Dental Hospital University of Barcelona (HOUB), to review the literature to spot the light on the different demographic data worldwide.MethodsThe archived panoramic image in the University of Barcelona dental Hospital were consecutively retrieved to investigate the prevalence of (ESP). Of all digital panoramic radiographs (OPG), 400 met the inclusion criteria and were furtherly analyzed. The results are correlated with the participant’s gender, age, and occurrence. Age is subcategorized into three groups. A chi-square test is used to measure the significant differences and the P-value is set at < 0.05 for the level of significance.ResultsAmong the included 400, we found 291 demonstrating (ESP). The prevalence of (ESP) which exceeds 30 mm is 72.75%. It is found that the most common morphological type is type 1 which is regarded as the uninterrupted (ESP) regardless of gender and age group. Concerning the calcification pattern, the most prevalent is the partial calcified (ESP) despite genders and age groups.Conclusion(OPG) is a sufficient tool for the screening of the elongated styloid process. Regarding the prevalence, our results are considered higher than previously reported prevalence in different populations using (OPG) radiography tool. A study on a wider spectrum of the Spanish population is recommended to further investigate the correlation between the elongated styloid process and the occurrence of Eagle’s syndrome.

A Case of Huge Congenital Cholesteatoma of Petrous Apex Treated With Translabyrinthine Marsupialization

Congenital cholesteatoma is rare, and especially so for a benign mass to grow from the squamous epithelium and the petrous apex as a location for this cancer. Surgery of the petrous apex cholesteatoma is challenging due to the location of the lesion and the need to preserve adjacent structures such as the dura mater, internal carotid artery, and internal auditory canal. Imaging studies, including CT and MRI, were crucial in guiding the surgical approach. This report describes a 40-year-old male patient with a large congenital cholesteatoma involving the petrous apex and temporal bone. The patient presented with a headache, hearing loss that persisted despite prior medical treatment. The cholesteatoma was surgically marsupialized through translabyrinthine approach, and the patient has remained stable for over 20 years. This report underscores the importance of considering the anatomical location and relationships of the lesion and adjacent structures when determining the surgical approach for congenital cholesteatoma involving the petrous apex and temporal bone.

Cholesteatoma of petrous bone: Auditory improvement with surgical treatment novel application of the posterior retrosigmoid approach

Introduction: Petrous Bone Cholesteatomas (PBCs) are epidermoid cysts, which have developed in the petrous portion of the temporal bone and may be congenital or acquired.

Combined retrosigmoid and middle fossa approach for a small, superiorly located petroclival meningioma: how I do it.

Petroclival meningiomas pose significant surgical challenges because of their deep location and complex surrounding neurovasculature. The use of multiple surgical approaches can optimize safe tumor removal from multiple anatomic compartments. We describe a patient with a growing superior petroclival meningioma centered at the posterior clinoid with extension into Meckel's cave that was successfully removed with a combined retrosigmoid and subtemporal middle fossa approach. This strategy avoided the need for anterior petrous bone drilling and tentorial splitting. A combined retrosigmoid and subtemporal middle fossa approach can provide safe access to tumors spanning the supra- and infratentorial compartments.

Anatomic Study of Petrous Bone and Its Surrounding Structures in the Extended Anterior Transpetrosal Approach.

Extended anterior transpetrosal approach (ATPA) includes drilling the petrous bone to achieve maximal exposure of the petroclival region. Injuring of surrounding neurovascular structures, such as the internal carotid artery (ICA), during the procedure may result in severe complications. In this study, we aimed to use computer topographic images to provide comprehensive anatomic information on the petrous bone and surrounding structures to help surgeons during the extended ATPA. Computer topographic angiography images of 110 individuals were reviewed, and measurements were performed on coronal, sagittal, and axial planes following multiplanar reformation. The petrous apex and sagittal midline were used to locate the anterior, middle, and posterior parts of the petrous bone and petrosal segment of the ICA during the ATPA. The thicknesses of the petrous bone were 3.28±0.71, 3.53±0.88, and 7.02±1.11mm at the petrous apex, trigeminal impression, and internal opening of internal auditory canal (IAC) positions, respectively. The distances between the petrous apex to the trigeminal impression, internal opening of the IAC, auris interna, and labyrinth were 7.39±1.62, 15.95±2.48, 17.39±2.39, and 29.00±3.18mm, respectively. Furthermore, the petrosal segment of the ICA was located at the above landmarks on the petrous bone. Our findings provide anatomic information on the petrous bone and surrounding structures during the extended ATPA procedure based on fixed anatomic landmarks so as to achieve maximal exposure and reduce the number of complications.

The comparative anatomy of the petrosal bone and bony labyrinth of four small-sized deer.

Here we provide complete 3D reconstructions of the petrosal bone and bony labyrinth of four kinds of small-sized deer (Elaphodus cephalophus, Muntiacus reevesi, Muntiacus muntjak, Hydropotes inermis) based on high-resolution CT scanning, and select one musk deer (Moschus moschiferus) as a comparative object. The petrosal bone and bony labyrinth of E. cephalophus are illustrated for the first time, as well as the petrosal bones of M. reevesi and H. inermis. Some morphological characters of petrosal bone and bony labyrinth can be used to distinguish the above-mentioned species. For example, M. moschiferus shows a prominent transpromontorial sulcus and a ventral basicapsular groove on the petrosal bone; there is a bifurcate cochlear aqueduct on the bony labyrinth of E. cephalophus; there is a distinct fusion between the lateral and posterior semicircular canals on the bony labyrinth of H. inermis. Meanwhile, there are some intraspecific variations on the subarcuate fossa, the tegmen tympani, the cochlear aqueduct, as well as the endolymphatic sac. Our results further confirm that the petrosal bone and bony labyrinth have enormous potential for taxonomy. This work will provide new anatomical data for the phylogenetic study of ruminants in the future, and it will be very practical to identify the isolated ruminants' petrosal bones that are frequently unearthed from paleontological or archeological sites.

Management of a challenging dura-embedded anterior inferior cerebellar artery loop during a retrosigmoid hearing-preserving vestibular schwannoma resection: microsurgical technique and operative video. Illustrative case.

Anatomical variants of the anterior inferior cerebellar artery (AICA), such as an anomalous "AICA loop" embedded in the dura and bone of the subarcuate fossa, increase the complexity and risk of vestibular schwannoma resections. Classically, osseous penetrating AICA loops are the most challenging to mobilize, as the dura must be dissected and the surrounding petrous bone must be drilled to mobilize the AICA away from the surgical corridor and out of harm. The authors present a rare case of a dura-embedded, osseous-penetrating AICA loop encountered during a hearing-preserving retrosigmoid approach in which they demonstrate safe and efficient microdissection and mobilization of the AICA loop without having to drill the surrounding bone. Although preoperative recognition of potentially dangerous AICA loops has been challenging, thin-sliced petrous bone computed tomography scanning and high-quality magnetic resonance imaging can be useful in preoperative diagnosis. Furthermore, this report suggests that a retrosigmoid approach is superior, as it allows early intradural recognition and proximal vascular control and facilitates more versatile mobilization of AICA loops.

A comparison between petrous bone and tooth, femur and tibia DNA analysis from degraded skeletal remains.

Skeletal remains are the only biological material that remains after long periods; however, environmental conditions such as temperature, humidity, and pH affect DNA preservation, turning skeletal remains into a challenging sample for DNA laboratories. Sample selection is a key factor, and femur and tooth have been traditionally recommended as the best substrate of genetic material. Recently, petrous bone (cochlear area) has been suggested as a better option due to its DNA yield. This research aims to evaluate the efficiency of petrous bone compared to other cranium samples (tooth) and postcranial long bones (femur and tibia). A total amount of 88 samples were selected from 38 different individuals. The samples were extracted by using an organic extraction protocol, DNA quantification by Quantifiler Trio kit and amplified with GlobalFiler kit. Results show that petrous bone outperforms other bone remains in quantification data, yielding 15-30 times more DNA than the others. DNA profile data presented likeness between petrous bone and tooth regarding detected alleles; however, the amount of DNA extracted in petrous bones allowed us to obtain more informative DNA profiles with superior quality. In conclusion, petrous bone or teeth sampling is recommended if DNA typing is going to be performed with environmentally degraded skeletal remains.

Sex determination by linear measurements of the bony labyrinth in cone-beam and computed tomography: a practical method.

The determinism of the sex is of most importance for reconstruction of the biological profile of deceased individuals. In this study, we aim to implement a technique to improve the accessibility of sex determination by the study of the bony labyrinth on cone-beam computed tomography (CBCT) and computed tomography (CT) scans. CBCT and CT scans of temporal bones performed between 2014 and 2022 were collected with demographic information. The width of the lateral (LSCw), posterior (PSCw), and anterior semicircular canal (ASCw) was measured. The primary outcome was the diagnostic performance of the individual linear measures and the product of these measures. This analysis is supplemented by establishing thresholds using ROC curves. Inter-judge and intra-judge reliability evaluation was performed blinded in randomly selected exams. One hundred forty-one petrous bones were included for analysis of their imaging. The analysis of the PSCw, ASCw, and ASCw*PSCw for sex determination was associated with area under curves of 0.88 ± 0.11, 0.82 ± 0.14, and 0.84 ± 0.10 respectively and accuracies of 0.74 ± 0.13, 0.78 ± 0.11, and 0.79 ± 0.13 respectively. In ROC-curve analysis, a PSCw*ASCw product > 48.5 allows to determine a male sex with > 95% specificity and a sensitivity of 50.1%. A PSCw*ASCw product ≤ 43 allows to determine a female sex with 88% specificity and 64% sensitivity. Reproducibility analyses showed good to excellent intra-judge and inter-judge reproducibility for ASCw and PSCw. Linear measurement of the semicircular canals of the vestibule on CBCT or CT could provide easy-to-use sex determination of the majority of females and males with a good predictive value.

Three dimensional structures of the inner and outer pig petrous bone using FIB-SEM: Implications for development and ancient DNA preservation

We report on the 3D ultrastructure of the mineralized petrous bone of mature pig using focused ion beam – scanning electron microscopy (FIB-SEM). We divide the petrous bone into two zones based on the degree of mineralization; one zone close to the otic chamber has higher mineral density than the second zone further away from the otic chamber. The hypermineralization of the petrous bone results in the collagen D-banding being poorly revealed in the lower mineral density zone (LMD), and absent in the high mineral density zone (HMD). We therefore could not use D-banding to decipher the 3D structure of the collagen assembly. Instead we exploited the anisotropy option in the Dragonfly image processing software to visualize the less mineralized collagen fibrils and/or nanopores that surround the more mineralized zones known as tesselles. This approach therefore indirectly tracks the orientations of the collagen fibrils in the matrix itself. We show that the HMD bone has a structure similar to that of woven bone, and the LMD is composed of lamellar bone with a plywood-like structural motif. This agrees with the fact that the bone close to the otic chamber is fetal bone and is not remodeled. The lamellar structure of the bone further away from the otic chamber is consistent with modeling/remodeling. The absence of the less mineralized collagen fibrils and nanopores resulting from the confluence of the mineral tesselles may contribute to shielding DNA during diagenesis. We show that anisotropy evaluation of the less mineralized collagen fibrils could be a useful tool to analyze bone ultrastructures and in particular the directionality of collagen fibril bundles that make up the bone matrix.

Chronically misdiagnosed Eagle's syndrome, treated through transoral styloidectomy: a rare case report.

A 39-year-old man who is a farmer and a driver was presented with complaints of ongoing, excruciating discomfort in the back of his left ear. Before the exam, he took a variety of drugs, various drugs 2 years without receiving a definitive diagnosis. Axial, coronal, and sagittal computed tomography scans of both petrous bones were analyzed, and the results showed aberrant styloid process elongation and calcification of the stylohyoid ligament. ES, shares many symptoms with other regional illnesses. Physicians frequently misdiagnose cases of ES and treat them without providing a conclusive diagnosis or treatment. ES diagnosis can be difficult for otolaryngologists and primary care providers due to its similarity with other regional illnesses. However, surgical intervention can result in consistent and significant symptomatic improvement when correctly diagnosed. The case presented in the report was successfully diagnosed as ES and treated surgically through transoral approach styloidectomy.

The M-Point A Novel Landmark in Middle Fossa Surgery: A Cadaveric Morphometric Study

The arcuate eminence (AE) is an anatomically consistent bony protrusion located on the upper surface of the petrous bone that has been previously studied as a reference for lateral skull base approaches. There is a paucity of information in the neurosurgical literature seeking to improve the safety of the extended middle cranial fossa (MCF) approach using detailed morphometric analysis of the AE. To evaluate the use of the AE as an anatomical landmark to help with early identification of the internal acoustic canal (IAC) in MCF approaches by means of a cadaveric study, using a new morphometric reference termed the "M-point." A total of 40 dry temporal bones and 2 formalin-preserved, latex-injected cadaveric heads were used. The M-point was established as a new anatomic reference by identifying the intersection of a line perpendicular to the alignment of the petrous ridge (PR), originating from the midpoint of the AE, with the PR itself. Subsequent anatomical measurements were performed tomeasure the distance between M-point and IAC.Additional distances, including PR length and the anteroposterior and lateral AE surfaces, were also measured. The mean distance between the M-point and the center of the IAC was 14.9mm (SD ± 2.09), offering a safe drilling area during an MCF approach. This study provides novel information on identification of a new anatomic reference point known as the M-point that that can be used to improve early surgical identification of the IAC.

How I do it: intradural anterior petrosectomy.

The anterior transpetrosal approach (ATPA) is a cranial base approach for addressing upper petroclival or lateral pontine lesions. It is fundamentally an epidural procedure involving the drilling of the petrous apex. However, this approach has significant procedure-related morbidity, and the surgeon must perform a complete petrosectomy, as the intradural structures are not in view during the drilling. For selected cases, a rationale exists for choosing a tailor-made intradural anterior petrosectomy (IAP). This article describes the relevant surgical anatomy and the different surgical steps of the IAP. IAP represents a feasible alternative to the standard ATPA with the advantage of minimizing the extent of petrous bone removal to the individual need.

Eye and hair color prediction of an early medieval adult and subadult skeleton using massive parallel sequencing technology.

Phenotypic trait prediction in ancient DNA analysis can provide information about the external appearance of individuals from past human populations. Some studies predicting eye and hair color in ancient adult skeletons have been published, but not for ancient subadult skeletons, which are more prone to decay. In this study, eye and hair color were predicted for an early medieval adult skeleton and a subadult skeleton that was anthropologically characterized as a middle-aged man and a subadult of unknown sex about 6years old. When processing the petrous bones, precautions were taken to prevent contamination with modern DNA. The MillMix tissue homogenizer was used for grinding, 0.5g of bone powder was decalcified, and DNA was purified in Biorobot EZ1. The PowerQuant System was used for quantification and a customized version of the HIrisPlex panel for massive parallel sequencing (MPS) analysis. Library preparation and templating were performed on the HID Ion Chef Instrument and sequencing on the Ion GeneStudio S5 System. Up to 21ng DNA/g of powder was obtained from ancient petrous bones. Clean negative controls and no matches with elimination database profiles confirmed no contamination issue. Brown eyes and dark brown or black hair were predicted for the adult skeleton and blue eyes and brown or dark brown hair for the subadult skeleton. The MPS analysis results obtained proved that it is possible to predict hair and eye color not only for an adult from the Early Middle Ages, but also for a subadult skeleton dating to this period.

A Computer Vision Algorithm to Classify Pneumatization of the Mastoid Process on Temporal Bone Computed Tomography Scans.

Pneumatization of the mastoid process is variable and of significance to the operative surgeon. Surgical approaches to the temporal bone require an understanding of pneumatization and its implications for surgical access. This study aims to determine the feasibility of using deep learning convolutional neural network algorithms to classify pneumatization of the mastoid process. De-identified petrous temporal bone images were acquired from a tertiary hospital radiology picture archiving and communication system. A binary classification mode in the pretrained convolutional neural network was used to investigate the utility of convolutional neural networks in temporal bone imaging. False positive and negative images were reanalyzed by the investigators and qualitatively assessed to consider reasons for inaccuracy. The overall accuracy of the model was 0.954. At a probability threshold of 65%, the sensitivity of the model was 0.860 (95% CI 0.783-0.934) and the specificity was 0.989 (95% CI 0.960-0.999). The positive predictive value was 0.973 (95% CI 0.904-0.993) and the negative predictive value was 0.935 (95% CI 0.901-0.965). The false positive rate was 0.006. The F1 number was 0.926 demonstrating a high accuracy for the model. The temporal bone is a complex anatomical region of interest to otolaryngologists. Surgical planning requires high-resolution computed tomography scans, the interpretation of which can be augmented with machine learning. This initial study demonstrates the feasibility of utilizing machine learning algorithms to discriminate anatomical variation with a high degree of accuracy. It is hoped this will lead to further investigation regarding more complex anatomical structures in the temporal bone.

Зависимость клинических проявлений паралитического лагофтальма от уровня и давности поражения лицевого нерва

The path of the facial nerve is associated with multiple nerves, bones and soft tissues, including n. trigeminus, n. intermedius, petrosal bone and parotid gland. Due to this fact, facial palsy results not only in lagophthalmos but also in dysfunction of tear production and even vision lost in some cases. The aim of the study is to compare clinical signs of lagophthalmos in patients with various levels and duration of facial palsy. We analyzed 120 cases of lagophthalmos in patients aged 5–90 y.o. with duration of facial palsy from 2 month to 90 years. The patients were divided into 4 groups according to the level of nerve damage: 1 – in the cerebral part of the nerve, 2 – in petrosal bone, 3 – in the area of parotid gland, and 4 – indefinite. The light forms of keratopathy were dominant in all of the groups (72.5 %). There was a very weak correlation between the duration of facial palsy and margin to the low limb distance (r = 0.190; p &lt; 0.05). The width of the eye fissure was significantly different between 1st and 3rd groups (p = 0.019), 1st and 4th groups (p = 0.042), 2nd и 3rd (p = 0.038), 2nd and 4th (p = 0.043). Although the results of Schirmer 1 tests was significantly different only between 1st and 3rd groups (p &lt; 0.001). Severity of clinical signs in paralytic lagophthalmos depends in most on the level of facial nerve damage and can be due to concurrent damage of n. trigeminus. The duration of the facial palsy and involvement of n. intermedius do not play any significant role. Keywords: n. facialis, n. trigeminus, n. intermedius, neurotrophic keratopathy, exposure keratopathy, exposure keratitis