A medical schematic diagram illustrating the neuroanatomical pathways of upper motor neurons (UMN) and lower motor neurons (LMN) and their selective involvement in Amyotrophic Lateral Sclerosis (ALS) variants. The diagram features a lateral view of the human brain, a coronal section of the brain, and transverse sections of the spinal cord (cervical and lumbar levels). Two primary tracts are highlighted: the corticobulbar (CB) tract, represented by green solid circles (UMN) and open circles (LMN), and the corticospinal (CS) tract, represented by blue solid circles (UMN) and open circles (LMN). Solid circles represent UMN cell bodies in the motor cortex, while open circles denote LMNs in the brainstem (bulbar) and spinal cord. Colored vertical tick marks inside these circles indicate specific disease phenotypes: red for classic ALS (CS & CB UMN and LMN), black for Primary Lateral Sclerosis (PLS, UMN only), and yellow for Progressive Muscular Atrophy (PMA, LMN only). Other variants shown include Pseudobulbar palsy (CB UMN), Flail arm, and Flail leg (specific CS LMN segments). This illustration serves as an educational tool for differentiating motor neuron disease phenotypes based on the anatomical site of degeneration.

This Comparison Diagram presents a cross-sectional illustration of the spinal cord, contrasting the localization of axonal spheroids and neuronal loss in Neuroaxonal Dystrophy (NAD) and Hereditary Spastic Paraplegia (HSP). The diagram is split into two halves: the left represents a Spanish Water Dog with NAD, and the right represents human HSP. Ascending sensory pathways are highlighted in red, including the Gracile Fasciculus (GF), Cuneate Fasciculus (CF), and Dorsal Horn (DH) on the NAD side, and GF, Dorsal Spinocerebellar Tract (DST), and Ventral Spinocerebellar Tract (VST) on the HSP side. Descending motor pathways, affected only in the HSP model, are highlighted in blue, depicting the Lateral Corticospinal Tract (LCT), Ventral Corticospinal Tract (VCT), and Ventral Horn (VH). The visual demonstrates that in NAD, pathology is restricted to sensory, ascending tracts in the dorsal funiculus and dorsal horn. In contrast, human HSP shows involvement of both sensory pathways and descending motor pathways (pyramidal tracts and ventral horns). This diagram illustrates the pathophysiology of upper motor neuron and sensory system degeneration relevant to neurology and neurohistology.

This clinical photograph set provides a side-by-side comparison of a 32-year-old female patient with chronic left-sided facial paralysis. The left image represents the baseline state three years post-TMJ surgery, showing classic signs of lower motor neuron facial nerve palsy. Key visible findings include left-sided brow ptosis, flattening of the horizontal forehead wrinkles on the left with compensatory overactivity on the right, widening of the palpebral fissure (lagophthalmos), and loss of the nasolabial fold. The oral commissure droops on the left, resulting in facial asymmetry during attempted expression. The right image shows the patient one month after extracellular vesicle (EV) treatment, demonstrating significant clinical improvement. There is a restoration of facial symmetry, improved resting muscle tone, and regained ability to perform a symmetrical smile. The nasolabial folds appear balanced, and brow positioning is more uniform. This comparison illustrates the recovery from severe facial nerve impairment (House-Brackmann scale) to mild dysfunction following therapeutic intervention.

This medical anatomical diagram provides a lateral view of the human brain, utilizing color-coding to delineate primary functional regions and lobes. The frontal lobe is highlighted in light blue at the most anterior position. Progressing posteriorly, the diagram identifies the motor cortex (purple) and the sensory cortex (yellow), which are separated by the central sulcus. The parietal lobe (yellow) follows posteriorly to the sensory cortex, while the occipital lobe is marked in pink at the most posterior pole. The temporal lobe is shaded in green, situated inferior to the frontal and parietal lobes. Below the occipital and temporal regions, the cerebellum is depicted with a distinct striated texture, contrasting with the gyri and sulci patterns of the cerebral cortex. The illustration is designed to teach regional brain anatomy and the spatial relationships essential for understanding corticomuscular coherence (CMC), movement planning, and tactile processing. The labels and color differentiation emphasize the distinct boundaries of these functionally specialized neural structures.

This diagnostic image provides a 3D lateral surface reconstruction of a human brain, derived from MRI data, highlighting cortical anatomy. The cerebral cortex is segmented into four primary lobes using a color-coding scheme: the frontal lobe is pink, the parietal lobe is yellow, the temporal lobe is green, and the occipital lobe is blue. The visualization emphasizes the complex patterns of gyri (elevated ridges) and sulci (grooves) that define human neuroanatomy. Visible landmarks include the central sulcus, which demarcates the frontal and parietal lobes, and the lateral fissure (Sylvian fissure), which separates the temporal lobe from the overlying frontal and parietal regions. This type of segmented anatomical diagram is used in clinical imaging research, such as the MIRIAD database studies, to quantify morphological changes like cortical tortuosity, atrophy, or surface area variations in neurodegenerative conditions such as Alzheimer’s disease. The reconstruction serves as a teaching tool for neuroanatomy and as a reference for volumetric and surface-based brain analysis.

This anatomical diagram provides a lateral view of the left cerebral hemisphere of the human brain, utilizing color-coding to differentiate major lobes and structures. The frontal lobe is highlighted in yellow, featuring the superior, middle, and inferior frontal gyri, as well as the precentral gyrus. The parietal lobe, shown in red, includes the postcentral gyrus, superior parietal lobule, supramarginal gyrus, and angular gyrus. The temporal lobe is shaded in pink, illustrating the superior, middle, and inferior temporal gyri. The occipital lobe is colored salmon, indicating the inferior occipital gyrus and occipital pole. Below the posterior lobes, the cerebellum is depicted in turquoise. The diagram uses thin leader lines to label specific cortical landmarks, including the frontal pole and the occipito-temporal gyrus. This visual serves as an educational tool for neuroanatomy, demonstrating the spatial relationships and surface morphology of the cerebral cortex, relevant for clinical neurology and functional magnetic resonance imaging (fMRI) correlation.

This composite of fluorescent micrographs illustrates axonal guidance defects in the corticospinal tract (CST) using DiI tracing in mouse models, specifically comparing Sema6A+/- (control-like) and Sema6A-/- (mutant) phenotypes. The images represent coronal cross-sections at five distinct neuroanatomical levels: the mid-hindbrain boundary (MHB) through the caudal medulla. In control mice (left column), CST axons follow a stereotyped medial and then ventral path toward the midline. In Sema6A-/- mutants (middle and right columns), multiple axonal routing abnormalities are visible: axons turning dorsally at the cerebral peduncle (blue arrowheads), aberrant midline crossing (yellow arrowheads), or splitting into disorganized bundles in the pons (magenta arrowheads). At the level of the inferior olive and caudal medulla (bottom rows), control axons maintain a tight midline position prior to decussation. Conversely, mutant axons often project laterally and proceed ipsilaterally (white arrowheads), failing to decussate. This neurodevelopmental study demonstrates the critical role of Semaphorin 6A signaling in hemming axons near the midline to ensure proper pyramidal decussation, with implications for understanding CST malformations like those seen in Joubert syndrome.

Educational medical graphic illustrating the tractography of the corticospinal tract (CST) in healthy controls and patients with DCC-related congenital mirror movements (DCC-CMM). Panel A provides an anatomical schematic and axial MR slices identifying Regions of Interest (ROIs) for fiber reconstruction: the base of the pons (a1), the anterior pyramid in the upper medulla (a2), and the cervical cord funiculus (a3). Crossed fibers are color-coded in light blue, and uncrossed fibers in red. Panel B displays coronal tractography at the level of the pyramidal decussation, superimposed on fractional anisotropy maps. It contrasts a healthy control, showing dominant light blue crossed CST (c-cst) fibers, with two DCC-CMM patients exhibiting a marked increase in red uncrossed CST (u-cst) fibers. Panel C presents a laterality coefficient graph, where controls show positive values (predominantly crossed fibers) and DCC patients show negative values (predominantly uncrossed fibers), highlighting the failure of normal axonal midline crossing in this condition.

This clinical endoscopic photograph captures an intraoperative view of a middle ear dissection, specifically identifying the anatomical relationship between the ossicles and the medial wall. The promontory (labeled 'P'), which corresponds to the basal turn of the cochlea, is visible as a darker, rounded bony prominence on the medial wall of the tympanic cavity. The malleus (labeled 'M') is shown in a state of detachment, displaced from its normal anatomical position relative to the tympanic membrane and other ossicles. A surgical instrument is visible at the top of the frame, manipulating the tissue to expose the middle ear space. The surrounding mucosa appears moist and light pink, with some fibrous tissue remnants near the tympanic annulus. This image serves as an educational tool for understanding otologic surgical anatomy and the visual identification of middle ear landmarks during endoscopic procedures.

Anatomical diagrams of the human ear and middle ear structures. Panel A is a detailed cross-sectional illustration showing the external ear (pinna, ear canal), middle ear (tympanic membrane, ossicles, eustachian tube), and inner ear (cochlea, semicircular canals, vestibular and cochlear nerves). Panel B provides a magnified view of the middle ear ossicular chain and supporting structures. It illustrates the anatomical relationship between the malleus (attached to the tympanic membrane), the incus, and the stapes (seated at the cochlear oval window). Key ligamentous supports are labeled, including the lateral mallear ligament (LML), superior mallear ligament (SML), superior incudal ligament (SIL), and posterior incudal ligament (PIL). The images serve to demonstrate the mechanical linkage responsible for transmitting acoustic energy from the external environment to the fluid-filled cochlea. The content is suitable for medical education regarding auditory anatomy and pathophysiology.

This anatomical diagram illustrates a transverse cross-section of the spinal cord and the subsequent formation and branching of a spinal nerve. The spinal cord is shown with its characteristic internal butterfly-shaped gray matter and surrounding white matter. Extending from the posterior and anterior aspects are the dorsal (sensory) and ventral (motor) roots, respectively. The dorsal root features a prominent dorsal root ganglion. These roots converge to form the mixed spinal nerve. The diagram details the primary distal branches of the spinal nerve, including the small recurrent meningeal branch, the dorsal ramus (supplying paraspinal structures), and the large ventral ramus (supplying the limbs and torso). Additionally, the image shows the rami communicantes (gray and white) connecting the spinal nerve to the sympathetic paravertebral ganglion, highlighting the integration with the autonomic nervous system. This educational illustration is designed to teach peripheral neuroanatomy and the functional pathways of spinal nerve distribution.

**Imaging Modality:** Computerized Tomography (CT) Myelography. **Anatomical Region:** Cervical spine, coronal reformatted view. **Observed Structures and Features:** The image displays a coronal cross-section of the spinal canal with intrathecal contrast enhancement. The spinal cord is centrally located, flanked by hyperdense contrast material within the subarachnoid space. High-resolution visualization demonstrates multiple bilateral ventral nerve rootlets arising from the spinal cord and traversing the subarachnoid space toward the neural foramina. **Key Findings:** - **Nerve Root Morphology:** The fine linear structures represent the ventral rootlets, appearing as discrete filling defects against the bright contrast. - **Bony Anatomy:** Adjacent vertebral bodies and pedicles are visible, providing anatomical orientation for segmenting the nerve roots. - **Pathology:** On the left side of the lower aspect of the image, there is evidence of traumatic nerve root avulsion, characterized by the absence of normal rootlet patterns and the presence of prominent pseudomeningoceles (extrathecal contrast collections) extending through the neural foramina. **Clinical Utility:** This imaging technique is utilized for the high-resolution assessment of preganglionic nerve root integrity and the diagnosis of brachial plexus injuries or root avulsions.