An Approach to Pupillary Disorders
Vivek Lal in A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
The pupillary constrictor muscle is innervated by the parasympathetic neurons. The preganglionic fibers originate in the ipsilateral Edinger-Westphal nucleus in the tectum of the midbrain. The fibers course ventrally through the midbrain to emerge in the interpeduncular fossa along with other fibers of the oculomotor nerve. These parasympathetic fibers remain dorsal and superficial throughout the course of the third cranial nerve in the subarachnoid space. Hence, these fibers are more susceptible to extrinsic compression (e.g., posterior communicating artery aneurysm) and relatively protected from ischemic insults as the vasa nervorum lies deep within the substance of the oculomotor nerve. These preganglionic parasympathetic fibers terminate in the ciliary ganglion within the orbit. Postganglionic parasympathetic fibers pass through the sclera as the short ciliary nerves and innervate the pupillary constrictor fibers (Figure 14.2). Activation of its muscarinic (M3) cholinergic receptors produces constriction or miosis of the pupil. An interesting anatomical fact is that only 3–5% of these fibers terminate in the iris sphincter muscle. The remainder terminate in the ciliary muscles that control accommodation [2]. The importance of this will be discussed later.
Histopathology
Peter D O Davies, Stephen B Gordon, Geraint Davies in Clinical Tuberculosis, 2014
If large numbers of bacilli are discharged into the pia arachnoid, a thick gelatinous exudate will form over the base of the brain. There may be tiny white granulomas along blood vessels. Microscopically, there will be a serofibrinous exudate in the basal meninges. Initially, there may be neutrophils, which are then replaced by mononuclear cells. A striking feature is infiltration of the walls of blood vessels by inflammatory cells causing vasculitis and caseous necrosis. There will be foci of caseation within the exudate but no well-formed granulomas. In the presence of severe hypersensitivity, there will be marked inflammation and necrosis. The inflammation extends along the blood vessels into the superficial cortex, resulting in small superficial infarcts in the affected cortex due to occlusion of the vessels. The thick exudate undergoes organisation as an attempt at healing and results in the formation of adhesions. The adhesions cause blockage of basal cisterns and the development of hydrocephalus (raised intracranial pressure). Adhesions around the interpeduncular fossa result in entrapment of cranial nerves that present clinically as cranial nerve palsies. The adhesions may also entrap vessels and cause stenosis of the internal carotid artery and the other basal cerebral vessels, which may already be involved by vasculitis, resulting in further ischaemia and subsequent brain infarction [55,56]. Rarely, TB bacilli may be discharged into the meninges from tuberculosis infecting a vertebral body or the choroid plexus.
Head and Neck
Bobby Krishnachetty, Abdul Syed, Harriet Scott in Applied Anatomy for the FRCA, 2020
The Circle of Willis lies in the interpeduncular fossa at the base of the brain, alongside the origins of many of the cranial nerves and represents the cerebral circulation. Anteriorly it is bordered by the optic chiasm and posteriorly by the pons. The arterial supply of the brain arises from the internal carotid arteries (70%) and the vertebrobasilar system (30%) (Figure 1.18).
Challenges and resources in adult life with Joubert syndrome: issues from an international classification of functioning (ICF) perspective
Published in Disability and Rehabilitation, 2022
Romina Romaniello, Chiara Gagliardi, Patrizia Desalvo, Livio Provenzi, Roberta Battini, Enrico Bertini, Maria Teresa Bonati, Marilena Briguglio, Stefano D’Arrigo, Maria Teresa Dotti, Lucio Giordano, Claudio Macaluso, Isabella Moroni, Sara Nuovo, Margherita Santucci, Sabrina Signorini, Franco Stanzial, Enza Maria Valente, Renato Borgatti
Joubert Syndrome (JS) is a rare inherited congenital cerebellar ataxia, with a prevalence of 0.5 per 100.000 in the overall population and 1.8 per 100.000 in the age range 0–19 years [1]. A peculiar cerebellar and brainstem malformation, named “the molar tooth sign” (MTS), represents the hallmark sign of the syndrome [2]. It is characterized by a deepened interpeduncular fossa with narrow isthmus and upper pons, thickened, elongated and misoriented superior cerebellar peduncles, and vermian hypoplasia/dysplasia, overall giving the appearance of a tooth on axial brain magnetic resonance imaging (MRI) [3]. JS is part of an expanding group of disorders called ciliopathies that are caused by the dysfunction of the primary cilium, an ubiquitous subcellular organelle which plays a key role in many tissues and during embryonic development [4]. JS typically manifests in neonatal age with hypotonia later evolving into ataxia, but the clinical phenotype of this syndrome is widely heterogeneous, and variably features retinal, renal, hepatic, skeletal and orofacial defects [5]. Although most affected children present intellectual disability and delay in the acquisition of psychomotor milestones, along the development the cognitive profile may present a wide spectrum, ranging from normal cognitive competences to severe intellectual disability [6–9]. Despite the latter being less frequent in JS than in other cerebellar malformations, specific impairments (e.g., language, working memory) impact on the cognitive profile and therefore on the everyday life and personal wellbeing of most JS individuals [10,11].
Wernekink commissure syndrome secondary to a rare ‘V’-shaped pure midbrain infarction: a case report and review of the literature
Published in International Journal of Neuroscience, 2020
Mingming Dong, Lishu Wang, Weiyu Teng, Li Tian
With the complex and richly supply to the midbrain, pure midbrain infarction is very rare (merely 0.6% in total ischemic stroke cases), and Wernekink commissure syndrome is even rarer [2]. Generally, there are four groups of arterial territories in the midbrain, including anteromedial (paramedian), anterolateral, lateral and dorsal arterial territory [3]. The paramedian area ranging from the thalamus to midbrain is mainly supplied by the interpeduncular fossa perforating branches that can be categorized into three groups based on the vascular supply territory [4]. The inferior paramedian mesencephalic arteries (IPMAs), one group of the interpeduncular fossa perforating branches, arising from the distal basilar arterial and proximal PCA or superior cerebellar artery, and supplying the region of caudal paramedian midbrain (CPM) including the Wernekink commissure, medial longitudinal fascicle (MLF), reticular formation and so on are commonly regarded as the culprit vessels of Wernekink commissure syndrome secondary to stroke [5,6]. Because of the anatomic variations of IPMAs, the morphology of caudal paramedian midbrain infarction (CPMI) on MRI can be various including oval, round and oblong shape [6]. However, in our case, an unusual ‘V’-shaped lesion was found. Previously, only two cases of Wernekink commissure syndrome with ‘heart or V’-shaped lesion have been reported [6,7]. Given that a one-hit pattern of onset was presented, the probable explanation for this shape lesion was the IPMAs with the variant branches supplying bilateral CPM [6].
Single piece fronto-temporo-orbito-zygomatic craniotomy: a personal experience and review of surgical technique
Published in British Journal of Neurosurgery, 2018
Manish Sharma, Sridhar Shastri
This approach using a single piece craniotomy has all the advantages of conventional FTOZ craniotomy used for skull base. It provides for a shorter trajectory to the lesions in para-sellar and interpeduncular fossa (Figures 4(A) and 5(A,B)). Its utility is however restricted in tumours extending to posterior fossa especially those involving middle and lower 1/3 of clivus. The need for temporal lobe retraction reduces remarkably (Figures 4(A) and 5(A)). The best approach to skull base remains the one that operating surgeon is most comfortable with, still single piece FTOZ craniotomy deserves a place in the armamentorium of every skull base surgeon and offers definite advantages especially in lesions with wide ant-post expanse and involving more than one compartment of skull base like sphenopetro-clival meningiomas. It gives a broader and shallower access with multidirectional approach and more than one corridor to the skull base.
Related Knowledge Centers
- Midbrain
- Oculomotor Nerve
- Pituitary Stalk
- Pons
- Tuber Cinereum
- Cerebral Crus
- Ventral Tegmental Area
- Optic Chiasm
- Posterior Perforated Substance
- Mammillary Body