KS results from defective neuronal migration of GnRH secreting neurons from the olfactory placode to the forebrain and hypothalamus, resulting in GnRH deficiency followed by LH and FSH deficiencies [2]. This decrease in the levels of gonadotropins was noted in our case. In a study conducted by Koenigkam-Santos et al. [3], it was found that the most common findings in KS patients were olfactory bulb and sulcus aplasia (85%). However, their data suggest that there is higher accuracy in predicting KS by evaluating the olfactory bulbs than olfactory sulcus. This is because, with olfactory bulb aplasia in some patients, different degrees of sulcus hypoplasia were demonstrated. Our case study’s findings, absence olfactory bulbs with hypoplastic olfactory sulci on both sides, correlate with the study mentioned above's findings. Developmental abnormality of the olfactory placode results in hypoplasia to aplasia of olfactory bulbs and sulci. Other associated anomalies, including various cardiovascular abnormalities, renal agenesis, cryptorchidism, short fourth metacarpal, and facial anomalies, have been reported [4]. These associated anomalies were not seen in our case.
MR imaging of the brain plays a vital role in the diagnosis of KS. Suzuki et al. [5] were the pioneers in describing the visualization of olfactory bulbs and tracts on MRI scans. The works by Yousem et al. [6] demonstrated that MRI could assess accurate volumetric measurements of the olfactory bulbs in various pathological conditions. This contribution had a high impact clinically because the olfactory bulb size and function closely correlate [7].
Optimal visualization of olfactory bulbs and tracts is with MR imaging through anterior fossa in the coronal plane. The sequences preferred for the olfactory system’s structural evaluation include high-resolution coronal fast spin-echo T2W and T1W images [8]. The normal anatomy of the region consists of olfactory bulbs located in the olfactory grooves, which run along with the cribriform plate and the olfactory sulcus in the inferior surface of the frontal lobes, separating the gyrus rectus from the medial orbital gyrus. These are the structures abnormal in KS. In our case, there was an absence of the olfactory bulb in the olfactory groove, and there was hypoplastic olfactory sulcus between the gyrus rectus and medial orbital gyrus on both sides. For perfect visualization of the olfactory bulbs, it is recommended that scanning in the coronal plane with large matrix size and decreased intersection gap is needed, demonstrating anatomical olfactory tract overview, detecting parenchymal lesions, and olfactory bulb volumetry [9, 8]. In some cases, there may be hypoplasia of anterior pituitary probably secondary to limited stimulation due to the absence of hypothalamic GnRH neurons. However, the anterior pituitary was normal in the present case.
In a study by Manara et al. [10], MR imaging was done on an outsized group of male KS patients using conventional and advanced sequences, including 3D-T1, FLAIR, and diffusion tensor imaging. Voxel-based morphometry, sulcation, curvature, and cortical thickness analyses and tract-based spatial statistics were performed, which showed significant brain changes specifically involving the gyri recti and the contiguous medial orbital-frontal regions. Even though further validation is warranted, this study has portrayed significant morphologic and structural brain changes that were likely driven by olfactory bulb hypo-/aplasia, selectively involving the basal forebrain cortex, which seemed to be is far more consistent than simple hypoplasia of the olfactory sulcus. These changes could not be assessed in the present case as the advanced techniques were not employed in the imaging.
Genetic testing is also employed in further evaluation of KS to detect the mutations in the respective genes. However, genetic testing was not done in the present case due to limited facilities. In this case, treatment is supportive, with exogenous sex steroids to restore normal pubertal development and, in some cases, normal fertility [11]