Traumatic chiasmal syndrome: a feature photograph

Traumatic chiasmal neuropathy results from injury to the face, sphenoid and clivus. Its pathogenesis remains enigmatic. Because of its close relationship to the pituitary gland, hypothalamus and internal carotid artery, a neuro-ophthalmic evaluation and imaging is needed in such cases. We present a patient who developed traumatic chiasmal syndrome after an automobile accident. Computed tomographic scan showed fracture of the sella turcica. A carotid angiography showed a traumatic pseudoaneurysm of the internal carotid at the base of the skull.

Traumatic neuropathies of the optic nerve, optic chiasm, and ocular motor nerves

This review focuses on traumatic chiasmal syndrome and traumatic neuropathies of cranial nerves II, III, IV, and VI. The review highlights common anatomical sites of injury to the above structures. Special emphasis is placed on review of recent literature. Other review of related material include.

[Ophthalmological symptoms of visual tract lesions in craniocerebral injuries]

Craniocerebral injuries are known to involve the visual tract in 2-5% of cases. Fifty-nine patients aged 5 to 68 with visual tract involvement in craniocerebral injury were examined in N. N. Burdenko Institute of Neurosurgery of the Russian Academy of Medical Sciences. Unilateral optic nerve involvement was found in 48 patients, involvement of the chiasm and/or both optic nerves in 11. Involvement of a single optic nerve was associated with vision acuity reduction, 30 patients becoming blind or virtually blind, and with various defects of the visual field. Traumatic injury to the chiasm manifested as a rule by the asymmetric chiasmal syndrome. Follow-up of the patients in the acute period of craniocerebral injury showed that paling of the optic disc manifested in various periods after the moment of the injury, from 3-4 days to 1 month, this depending on the localization of the injury and its distance from the posterior pole of the eye. Besides visual disturbances and ophthalmoscopic changes, oculomotor disorders were found which were caused by traumatic impairment of the oculomotor nerves (in the orbit or skull) and muscles. Transcutaneous electrostimulation of the injured optic nerves was sufficiently effective, its efficacy directly depending on the period elapsed since the injury, excepting blind or virtually blind patients.

Electrodiagnostics of chiasmal compressive lesions

Recording of visual evoked potentials (VEPs) is not yet a routine test in patients with suspected chiasmal compressive lesions, but has proved useful to a clinician in assessing and following-up visual pathway dysfunctions. Abnormalities of VEPs can be found even in patients without clinical evidence of the visual impairment: VEP delays and alterations of the waveform, asymmetric distribution in one eye or in both eyes (crossed asymmetry) can indicate chiasmal compressive lesion. Simultaneous recording of pattern electroretinograms (PERGs) can additionally provide useful information about the patient's cooperation as well as about eventual retrograde degeneration of the ganglion cells. Electrophysiologic tests can be regarded as an integral part of diagnostic procedures--ocular diagnostic tests and neuroimaging--in suspected compressive lesions of the optic chiasm.

Traumatic chiasmal syndrome associated with midline basilar skull fractures

We studied two young males who had visual field defects consistent with optic chiasmal injury after blunt frontal head trauma. One patient also had a unilateral optic neuropathy. Long-term follow-up disclosed complete bi-temporal hemianopsias in these patients. Both patients had midline basilar skull fractures that traversed the midclivus through the sella turcica floor, dorsum sellae, and sphenoid sinus. Magnetic resonance images did not identify intrachiasmal hemorrhage as the cause of the visual field defect. We believe this fracture pattern, in conjunction with the magnetic resonance image findings, suggests tearing of the optic chiasm on a microscopic, if not macroscopic, scale as the cause of the complete bitemporal hemianopsia.

Chiasmal trauma: clinical and imaging considerations

This report presents a patient who sustained closed head injury with chiasmal trauma. This uncommon injury may not be apparent on routine imaging studies. It is significant, not only from the visual standpoint, but also because of the association with serious conditions, such as panhypopituitarism, traumatic carotid aneurysm, carotid cavernous fistulae, and meningitis associated with leakage of cerebrospinal fluid. This report demonstrates that magnetic resonance imaging (MRI) is the best method for identifying chiasmal abnormalities.

[Traumatic avulsion of the optic nerve in the chiasm region]

Avulsion of the optic nerve in the chiasmal region is a very rare injury. The authors presented a case of such avulsion with concomitant temporal visual field defect in the other eye. The pathomechanism of this type of optic nerve injuries is discussed.

Post-traumatic chiasmatic disruption

Ten patients with traumatic disruption of the optic chiasm are presented. The clinical sequence of fronto-facial trauma and CSF rhinorrhoea, followed days later by diabetes insipidus and discovery of a bi-temporal visual field loss constitute a characteristic syndrome which should be recognized by the attending medical staff. Magnetic resonance imaging, not previously reported, and post-mortem evidence point to a physical disruption of the chiasm and infundibulum as the cause of the visual and hypothalamic signs. The resulting field defect is permanent but the diabetes insipidus is transient in 50% of patients and can be adequately managed with manipulation of the patient's fluid intake.

Traumatic lesions of the suprasellar region: MR imaging

The authors studied nine patients with injuries to the suprasellar region with 1.5-T magnetic resonance (MR) imaging. Five patients had chiasmal injuries diagnosed by means of clinical examination. MR imaging demonstrated complete transection in two of these five patients, contusion of the chiasm by inferior herniation of the gyrus rectus in one, and a normal chiasm in two. Two patients had large tears of the floor of the third ventricle resulting in wide communication between the third ventricle and the prepontine cistern. One of these patients also had an avulsed third nerve. Transection of the pituitary stalk was seen in two patients. MR imaging can demonstrate injuries to the suprasellar structures. The MR imaging appearance of optic chiasm correlates with different types of injury to the chiasm described in the clinical literature and may alleviate the need for additional diagnostic studies to help explain the patient's symptoms.

Visual abnormalities with multiple trauma

The diversity of pathogenetic mechanisms involved in posttraumatic visual impairment was reviewed in a study of the hospital records of 24 patients admitted with multiple injuries. Most major visual abnormalities occurred in young people (average age 33 years) who presented with a wide range of overall severity of injury (injury severity score 13-47) and involvement of the central nervous system (Glasgow coma scale 5-15). Bilateral or monocular blindness developed in 63% of patients. Seventy percent of the injuries involved the anterior visual pathways with damage to the optic nerve alone accounting for 35%. Fractures of the sphenoid bone, particularly of the body, accompanied optic nerve and chiasmal injuries and some cases of traumatic carotid-cavernous fistulas. Pathogenetic mechanisms varied according to the site of injury and included vitreous hemorrhage and optic atrophy secondary to raised intracranial pressure, retinal hypoxia from carotid-cavernous fistulas, shearing and compression injuries of the optic nerve, traumatic chiasmal syndrome, temporoparietal and occipital contusions, and transtentorial herniation with occipital infarction. Visual abnormalities varied in severity from moderately reduced visual acuity and diverse hemianopias and scotomas to blindness. The incidence of posttraumatic residual visual abnormalities is likely to increase in the wake of improved acute care of the traumatized victim.

Receptive field sizes and responsiveness to light in area 18 of the adult cat after chiasmotomy. Postoperative evolution; role of visual experience

Receptive field sizes to stimulation of the ipsilateral temporal retina were studied in area 18 of adult cats at different times after complete midsagittal section of the optic chiasm. A specific postoperative evolution could thus be noticed: immediately after section, the average area of the receptive fields was reduced, as compared to control preparations, owing to the disappearance of large fields located at more than 20 degrees of eccentricity. A progressive reappearance of these large fields occurred between 8 and 45 days after chiasmotomy, provided that the animal was placed in normal visual conditions during its postoperative period. No such recovery could be assessed after as long as 55 days, in animals kept in complete darkness after operation. Chiasmotomized cats also displayed a reduction of their percentage of light reactive cells with respect to controls, as expected from the suppression of the contralateral input. This percentage was at first very low and progressively increased, during postoperative recovery but again not when the animal had been kept in the dark. Finally, an increase of cells with "diffuse responses" was observed in the late postoperative recovery stage. This latter evolution also appeared to depend upon postoperative visual experience. On the other hand, no clear indication of an interhemispheric transfer could be obtained in these experiments, even at the 17-18 boundary.

Traumatic chiasmal syndrome

We studied 11 patients with the uncommon finding of traumatic chiasmal syndrome after closed head trauma. Visual field defects varied from complete monocular blindness and contralateral temporal hemianopia to subtle bitemporal arcuate scotomas. The degree of visual loss was not necessarily related to the severity of the craniocerebral trauma. Diabetes insipidus was present in half of these patients, but unlike the visual abnormalities, this complication was transient.

Visual abnormalities after severe head injuries

The authors studied 12 patients with major abnormalities of the afferent visual system following closed injury to the head. The anatomic sites of injury were the eye in five patients, the optic nerve in seven patients, the chiasm in four patients and the optic radiations in four patients. A technique for rapid evaluation of the afferent visual system in patients with multiple injuries is presented. Three representative examples of permanent visual loss following closed head injury are reported.

[Avulsio bulbi (author's transl)]

It is reported about a 14 year old girl, sustaining an avulsion of the left eye-ball by a coat-rack. The optic nerve was cutted 18 mm retrobulbarly. In perimetry of the fellow-eye a temporo-superior defect was found as proof of traumatisation of the anterior-loop-fibers in the chiasm.

Traumatic bitemporal hemianopsia: case report

Bitemporal hemianopsia due to trauma to the optic chiasm is uncommon following head injury. In the patient described, a hemianopic field defect was seen 12 days after frontal basilar skull fracture. We feel the cause is intrachiasmatic contusion, edema, and hemorrhage. Serial ophthalmologic examinations and possibly use of steroids are recommended.

Traumatic hypopituitarism associated with bitemporal hemianopia in a prepuberal child

The case of a boy affected by post-traumatic hypopituitarism associated with bitemporal hemianopia is described. While traumatic bitemporal hemianopia is not an extraordinary occurence, traumatic injuries have been rarely reported among the causes of hypopituitarism. This may be because the cranial trauma in most of the cases is too severe to permit survival. After having considered the diagnostic problems the authors briefly review the peculiar vascular supply to the chiasma and anterior diencephalon and try to consider the pathogenetic mechanism of the syndrome. Direct contusion necrosis and direct intraparenchymal hemorrage in the chiasma and in the hypophysis or hypothalamus are considered the most probable causal factors; however, the concomitant occurence of chiasmal and hypopituitary injury might be explained by a single transient compressive mechanism either on the tubero-hypophysial arteries or on the smaller vessels of the infundibular network. The difficulty of ascertaining both the pathogenetic mechanism and the seat of the endocrine lesions on the basis of the clinical signs is stressed.

[Traumatic lesions of the optic chiasma (author's transl)]

Traumatic lesions of the chiasma are few when one considers its anatomical position. They happen after severe direct or indirect traumas with or without skull fractures, and with or without macroscopic lesions. Microscopic lesions are characterised by contusion. Clinically the visual loss goes together with bitemporal defects and with bilateral hemorrhagic papillar oedema. Early complications are hematoma of the optochiasmatic space and perichiasmatic meningitis: among delayed complications optochiasmatic arachnoiditis prevails.