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An Approach to Pupillary Disorders
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Sarosh M. Katrak, Azad M. Irani
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.
Head and Neck
Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
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).
Histopathology
Published in Peter D O Davies, Stephen B Gordon, Geraint Davies, 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.
Meckel Gruber and Joubert Syndrome Diagnosed Prenatally: Allelism between the Two Ciliopathies, Complexities of Mutation Types and Digenic Inheritance
Published in Fetal and Pediatric Pathology, 2022
Somya Srivastava, Rani Manisha, Aradhana Dwivedi, Harshita Agarwal, Deepti Saxena, Vinita Agrawal, Kausik Mandal
Joubert syndrome was initially characterized by ataxia, intellectual disability, abnormal eye movements, agenesis of cerebellar vermis and occasional hyperpnea [14]. Agenesis of cerebellar vermis along with deep interpeduncular fossa gives rise to the “molar tooth sign” on MRI brain. This characteristic sign was delineated in 1997 [15]; several years after the first description of the syndrome in 1969. The molar tooth sign was identified in several disorders and the term ‘Joubert syndrome related disorders’ was coined to encompass all defects with molar tooth sign. This syndrome was further subdivided into six clinical types depending upon the presence or absence of additional features: pure Joubert syndrome, JS with ocular defect, JS with renal defect, JS with oculorenal defect, JS with hepatic defect, and JS with orofaciodigital defect highlighting the clinical heterogeneity of this syndrome [16]. Presently, 36 causative genes have been identified [3].
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].
Complete third nerve palsy as a presenting feature of an interpeduncular lipoma
Published in British Journal of Neurosurgery, 2021
Lucy E. James, Stuart A. G. Roberts, Radu Beltechi, Rahim Hussain
Reports of IIIrd nerve palsy precipitated by intracranial lipomas are rare. On review of the literature, two prominent cases are described.4 reported a male patient with intermittent partial IIIrd nerve palsy associated with intracranial lipoma. However more detailed analysis suggested this might be due to a malformation of the IIIrd nerve itself.3 reported a case of a 23-month-old male patient presenting with sudden onset left-sided, complete IIIrd nerve palsy, involving the pupil. MRI revealed a left unruptured interpeduncular fossa lipoma. There was spontaneous yet gradual improvement of symptoms, however follow-up MRI demonstrated that there was no change in the size of the lipoma. A further patient had gradual and spontaneous improvement of symptoms, with complete resolution reported at the 4-month follow-up visit in spite of a second MRI at 6 months showing that the lipoma had not changed in size.3