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Dilated perivascular spaces in the putamen and pallidum in patients with Parkinson's disease scheduled for pallidotomy: a comparison between MRI findings and clinical symptoms and signs.

Forty patients with Parkinson's disease without mental deterioration who were scheduled for ventroposterolateral (VPL) pallidotomy were randomly selected for retrospective stereotactic magnetic resonance image (MRI) analysis. The preoperative MRI study was performed on a 1.0-T MRI machine with a three-dimensional gradient-echo sequence. The MRI analysis was focused on five consecutive 2 mm thick axial slices without gap and parallel to the intercommissural line, starting from the level of the foramen of Monro and continuing in a ventral direction. Lacunar cysts of varying sizes (4-424 mm3) were seen at least in one hemisphere of all patients. The cysts had a clear dominance in posteroventral regions of the lateral-most pallidal regions (GP) and posteroventral regions of the putamen (PUT). No statistical correlation was found between the number or volume of the cysts and the sex, age, or duration of illness of the patients. Patients with predominantly left-sided clinical symptoms had a concentration of the cysts in the left GP, whereas those with predominantly right-sided symptoms had cysts significantly larger and more frequent in the right than the left GP. The cysts did not seem to affect the clinical outcome of pallidotomy. The authors think striatopallidal cysts develop from dilated perivascular spaces of the lenticulostriate vessels in the posteroventral regions of the GP and PUT. They are not pathognomonic for PD, but they may play some role in lateralization of the clinical symptoms in this classically asymmetric condition.

Aged↗

[Marchesani's syndrome (spherophakia-brachymorphism)].

The authors report the case of a patient with spherophakia and brachymorphism (Marchesani syndrome). This congenital and familial disorder is characterized by short stature, short limbs and thick extremities, limitation of joint mobility, a peculiar facies and spherophakia (rounded lens). Mentality is normal. The patient presented here, an eleven-year-old girl, had in addition a subvalvular fibromuscular aortic stenosis. A detailed radiological survey of the skeleton demonstrated a disorder of enchondral growth, particularly evident in the extremities, with short and wide diaphyses, thin cortical bone, and relatively discrete epiphyseal deformities. The vertebral bodies were slightly rounded anteriorly, th discs were thinned, and the ribs widened. The spinal canal and the foramen magnum were narrowed, and the lateral processes short and wide. There was thickening of the skull vault. A mucopolysaccharidosis and a mucolipidosis were excluded by biochemical study of skin fibroblasts in culture.

Abnormalities, Multiple↗

Neural symmetry and functional asymmetry of the mandible.

Even in the absence of malformation or skull base asymmetry, the mandible may be physiologically asymmetric and this remains a major challenge in the orthodontic treatment. The mandible is a bone formed by a primary subunit, i.e., the neural part, with different functional secondary subunits, so we suggest that in a normal mandible the asymmetry was caused by the secondary functional subunit and the neural part is nearly symmetric. Eighty-three dry human mandible samples were studied. The measurements of the size of the mandible (corpus, ramus, mandible notch, condylar process, the angle of the mandible) and the neural subunit (the mandibular canal and the position of the mental and mandibular foramina) were measured bilaterally. The left and right sides were compared according to the dental status: 60 dentate and 23 edentulous mandibles. The calculation of the symmetry was based on the paired Student t test, the absolute difference |R-L| and the relative absolute difference |R-L|/|R+L|x100. The mandibular canal and the position of the foramina were symmetric, except for the position of the mandibular foramen in relation to the mandible notch. The symmetry was not modified by the dental status. The total length of the mandible and the length of the ramus were greater on the left side independently from the dental status. The length of the corpus and the mandible angle were symmetric in each group. The mandible notch was always asymmetric and its height was greater in the dentate group. The condylar process was the most asymmetric structure in each group. The primary subunit of the mandible, surrounding the mandibular canal, is a symmetric component of the mandible and is not modified by the dental status. The angle of the mandible between the corpus and ramus is another symmetric parameter that is important for the facial architecture. The ramus and especially the mandibular notch as well as the condylar process are the most asymmetric subunits influenced by the functional matrices.

Analysis of Variance↗

Intermanual information transfer in patients with lesions in the trunk of the corpus callosum.

Interhemispheric transfer of haptic information was examined in six partially callosotomized patients and three control subjects. Three different portions of the trunk were severed in different subjects. The most anterior 10 mm of the trunk, anterior to the foramen of Monro, was sectioned in one patient. Three other patients had lesions restricted to the anterior part of the trunk posterior to the foramen of Monro. The posterior third of the trunk was damaged in two patients. The splenium, genu and rostrum of the corpus callosum were intact in all six patients, as were the anterior and hippocampal commissures. Poor transfer of haptic information was found only in the three patients with the lesion located in the anterior part of the trunk posterior to the foramen of Monro. The functional anatomy of this region is discussed. It is assumed to house fibers responsible for interhemispheric transfer of complex tactile information.

Adolescent↗

Mechanisms of basilar skull fracture.

Basilar skull fractures comprise a broad category of injuries that have been attributed to a variety of causal mechanisms. The objective of this work is to develop an understanding of the biomechanical mechanisms that result in basilar skull fractures, specifically focusing on mandibular impact and neck loading as potential mechanisms. In the characterization of the injury mechanisms, three experimental studies have been performed. The first study evaluated the response of the base of the skull to midsymphysis loading on the mental protuberance (chin) of the mandible. Five dynamic impacts using a vertical drop track and one quasi-static test in a servohydraulic test frame have been performed. In each test, clinically relevant mandibular fractures were produced but no basilar skull fractures were observed. The second study assessed the fracture tolerance of the base of the skull subject to direct loading on the temporomandibular joint in conjunction with tensile loading imposed locally around the foramen magnum to simulate the effect of the ligaments and musculature of the neck. Among four specimens that sustained either complete or incomplete basilar skull ring fractures remote from the sites of load application, the mean load at fracture was 4300 +/- 350 N. Energy to fracture was computed in three of those tests and averaged 13.0 +/- 1.7 J. Injuries produced were consistent with clinical observations that have attributed basilar skull ring fractures to mandibular impacts. In the third series of experimental tests, loading responses resulting from cranial vault impacts were investigated using unembalmed human cadaver heads and ligamentous cervical spines. Multiaxis load cells and accelerometers, coupled with high-speed digital video, were used to quantify impact dynamics. The results of these experiments suggest that while there is a greater probability of cervical spine injury, basilar skull ring fractures can result when the head is constrained on the impact surface and the inertia of the torso drives the vertebral column onto the occiput.

Biomechanical Phenomena↗

Generation of far field potentials from the trigeminal nerve in the cat.

This study provides evidence that far field potentials (FFPs) are generated from the trigeminal nerve in the cat. By stimulating the main mental nerve, three components (component 1, 0.59 +/- 0.06 ms; component 2, 0.81 +/- 0.06 ms; and component 3, 0.98 +/- 0.07 ms) were identified from surface electrodes. These three components were thought to be positive and negative FFPs because each component had a stationary peak and was distributed on the head being divided into positive and negative fields. Results of a study of lesions and recording compound action potentials (CAPs) defined the neural origins of those potentials as follows: component 1, the mandibular nerve at the mandibular foramen; component 2, the mandibular nerve at the foramen ovale; and component 3, somewhere between the gasserian ganglion and the trigeminal root. The amplitude of component 2 decreased when the mandibular nerve at the foramen ovale was immersed in cerebrospinal fluid (CSF) after opening the foramen and recovered to the prior level after closing the foramen with beeswax. We concluded that this transformation resulted in the change in electrical resistance of the volume conductor around the nerve.

Action Potentials↗

[Solitary subependymal giant cell astrocytoma: a forme fruste of tuberous sclerosis complex?].

Subependymal giant cell astrocytoma (SEGA) is usually associated with tuberous sclerosis (TS) and believed to originate from subependymal nodules. We report a rare case of SEGA in a patient lacking symptoms of TS. Radiological findings, including CT and MRI, were characteristic of SEGA, but the preoperative diagnosis was difficult due to the fact that no other features of TS were present. TS has been classically characterized by the clinical presence of Vogt's triad of seizure, facial angiofibroma and mental retardation, however, few cases present with all of these manifestations. In 1998, Roarch et al. proposed new clinical diagnostic criteria for the TS complex based on the clinical and radiographic features of TS. According to these criteria, our case is classified as a "possible" TS complex. There have been previous reports of SEGAs without any obvious features of TS, but it is still controversial as to whether these reports represent a forme fruste of TS. To determine a strict diagnosis of SEGA, additional genetic studies are needed. The possibility of SEGA should be considered whenever an intraventricular tumor near the foramen of Monro is found, regardless of other clinical features of TS.

Adult↗

[Fronto-ethmoïdal encephaloceles in Dakar. Report of 9 cases].

A retrospective study of 9 cases of fronto-ethmoïdal encephaloceles is reported. Cases have been gathered from the files of Dakar University Neurosurgical Unit. Fronto-ethmoïdal encephaloceles were about 9.8% of all encephaloceles. In all the cases the exit hole from the anterior cranial fossa is at the site of the foramen caecum. The location of the tumor was fronto-nasal in seven patients and naso-ethmoïdal in two. The cranio-facial deformity consisted of increase of local volume and a lateral displacement of medial canthus in six cases, a down ward drift of the tip of the nose in two cases and one case of orbital hypertelorism. Eight cases were meningo-encephaloceles and the last a meningo-encephocystocele. Diola was the most ethnic group involved. All patients have been operated by a simple neurosurgical procedure without obstruction of the cranial defect nor bony displacement. In five cases mental and aesthetic results were good when operation was done during the first year of live. The authors stress early surgical treatment for fronto-ethmoïdal encephaloceles.

Child, Preschool↗

Colloid cysts of the third ventricle. A review of 36 cases.

Thirty-six colloid cysts were treated from 1949 to 1983. There were 26 male and 10 female patients, ranging in age from 12 to 65 years old, 60% between 31 and 40 years. Headache or disturbed mental function was the most frequent complaint, papilloedema the most frequent sign. The patients were classified into 3 groups by symptoms and signs; Group I (17 patients): Headache, papilloedema and no neurological signs. Group II (6 patients): Fluctuating or progressive dementia. Group III: Twelve cases with "classical" features, episodic headache and drop attacks. One patient could not be classified in any of these groups. Seventeen of 36 patients were diagnosed by ventriculography, 19 patients were diagnosed by CT scan. CT scan was the most reliable diagnostic study, but was unavailable in the earlier part of the series. All patients have been operated by transventricular exposure of the right foramen of Munro with incision of the middle frontal gyrus in an antero-posterior linear manner. Twenty-five of 36 patients showed an excellent operative result, and nine had a good result, one of the 9 patients dying of an unrelated intracerebral haemorrhage 4 years after operation. Two patients had a poor result, characterized by memory loss and confusion. One of these died of an unknown cause 5 years after operation.

Adolescent↗

Topographic anatomy of the lingual nerve and variations in communication pattern of the mandibular nerve branches.

We made a thorough observation of the morphology and course of the lingual nerve (LN) and inferior alveolar nerve (IAN) to clarify their topographical relationships in the infratemporal fossa and in the paralingual area. Thirty-two Korean hemi-sectioned heads were dissected macroscopically and microscopically from a clinical viewpoint. On the 32 tracings on the radiograph, the average distance between the retromolar portion and the LN was 7.8 mm, and no case was found where the LN ran above the alveolar crest as passing along the mandibular lingual plate. The bifurcation of the LN and IAN was located around the mandibular notch, inferior to the otic ganglion in 66% of the cases, and a plexiform branching pattern of the mandibular nerve was observed in only two cases. The bifurcation spot of the LN and IAN was located 14.3 mm inferior to the foramen ovale and 16.5 mm superior to the tip of hamulus. Collateral nerve twigs from the LN to the retromolar area were observed in 26 cases (81.2%), with an average of one nerve twig. We observed four types of variations in terms of communication pattern. In four specimens, the mylohyoid nerve passed through the mylohyoid muscle and connected with the LN. In other four specimens, the IAN communicated with the auriculotemporal nerve. We also observed another type of variational communication between the IAN and the nerve to the lateral pterygoid (LPt); this was observed in only one specimen, and it could be predicted that motor innervation from the nerve to the LPt was transmitted via the mental nerve to the depressor anguli oris. Another type was observed where the IAN divided into two branches with the posterior branch being partially entrapped by the LPt muscle fibers.

Adult↗

[Tuberous sclerosis with intraventricular tumor: report of 2 cases].

It is well known that intraventricular tumors are occasionally seen in patients with tuberous sclerosis. We have experienced two cases of tuberous sclerosis with intraventricular tumor. Case 1: an 8-year-old girl was admitted to our clinic because of headache and vomiting of one month's duration. She had adenoma sebaceum, mental retardation and seizures clinically, and a large tumor was found in the right lateral ventricle by pneumoventriculography. Partial removal of the tumor was performed by the right frontal transcortical approach, but she later died of pneumonia. Necropsy revealed hamartomatous disease characterized by multiple focal tumor-like malformations in various organs including the brain, kidneys, heart, lungs and liver. The histological diagnosis of the intraventricular tumor was subependymal giant cell astrocytoma. Case 2: a 6-year-old boy was admitted to our clinic because of headache of one year's duration. He had also suffered from seizures since 6 months of age. Adenoma sebaceum was noted in the cheeks. CT revealed a medium sized tumor at the right foramen of Monro and the moderately dilated right lateral ventricle and several calcified deposits in the lateral ventricle wall. The tumor was subtotally removed by the right frontal transcortical approach. The pathological examination showed subependymal giant cell astrocytoma. Now 6 years after the operation he is enjoying a normal school life. In our cases, intraventricular tumors associated with tuberous sclerosis were of a typically benign histological appearance, that is subependymal giant cell astrocytoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Astrocytoma↗

Subependymal giant cell astrocytoma: clinical and neuroimaging features of four cases.

The clinical history, neuroimaging features, treatments, and outcome of 4 patients with histologically verified subependymal giant cell astrocytomas (SEGA) were retrospectively reviewed. The average age at the time of surgery was 13.3 years. Headache related to raised intracranial pressure was the first and only sign in 2 patients, with the remaining 2 being admitted because of sequential neuroimaging studies over several years revealing the growth of 'subependymal nodules' into intraventricular tumours. In each case the tumour was in the region of Monro's foramen and was associated with ventricular dilatation. On computed tomography (CT), multiple subependymal nodules were found in 3 patients, and these well circumscribed isodense SEGAs were markedly enhanced by contrast medium. On magnetic resonance imaging (MRI), which was obtained in 3 patients, 2 SEGAs were isointense with the cerebral cortex and one with the white matter on T1-weighted images, and on T2-weighted images, 2 were isointense with the cortex and one with the white matter. At surgery the tumours appeared to originate from the inferolateral wall of the lateral ventricle in the region of the head of the caudate nuclei. Total macroscopic removal was achieved in 3 patients, and subtotal removal in one patient. Follow up ranged from 4.6 to 13.2 years, and all patients have exhibited similar physical and mental conditions to preoperative. So far there has been no evidence of any recurrences. The diagnosis and the surgical indications for SEGA are discussed, with periodic monitoring with neuroimaging studies being recommended even for asymptomatic patients with 'subependymal nodules'.

Adolescent↗

Venous air embolism during home infusion therapy.

Venous air embolism (VAE) is a potential complication of surgical procedures as well as central venous access. There are several reports in the literature of VAE during the in-hospital use and placement of central venous access. However, we are unaware of previous cases of VAE in children who received home infusion therapy via central venous access. We report the occurrence of a VAE in a 2-year-old with a Broviac catheter for home intravenous antibiotic therapy. VAE occurred when a bolus of air was unintentionally administered as the mother removed the cassette from the pump when it was alarming air in line. The cassette and tubing had been placed into the pump without a fluid flush. After the tubing and cassette were removed from the pump, the air in the line was allowed to flow by gravity into the patient, resulting in the immediate onset of respiratory and neurologic symptoms. The mother administered 2 rescue breaths, and the child's color and breathing returned to normal over the next 2 minutes. After the child arrived in the emergency department, the child's mental status returned to normal and the remainder of her physical examination was unremarkable. She had an uneventful recovery and was discharged from the hospital the following day. Additional antibiotic administration was accomplished in the emergency department of a local hospital. VAE can occur spontaneously when there is an open venous structure 5 cm or more above the heart or if air is delivered under pressure into the venous system, such as during a laparoscopy or mishaps with infusion bags. The morbidity and mortality of VAE are related to the volume of air, rate of entrainment, the patient's underlying cardiorespiratory status, and the patient's position. Morbidity and mortality occur as a consequence of right ventricular outflow obstruction or end-organ dysfunction from left-sided obstruction of coronary or cerebral vasculature as air passes across a patent foramen ovale or through the pulmonary circulation. Of all the literature pertaining to VAE with central lines, there are no previous reports of VAE occurring during home infusion therapy in children. With managed care requiring shorter hospitalizations and more children being discharged from the hospital on home infusion therapy, parents and lay caregivers are being asked to administer medications and perform routine maintenance on central venous devices. In our case, despite the fact that the mother had been educated regarding the appropriate technique for medication administration, she forgot to purge the air from the line before connecting the tubing and administering the antibiotic. Although the infusion pump will alarm when there is air in the line, it detects air only in a small part of the line and this safety feature is not in play if the device is removed from the infusion pump and administered via gravity. If such safety precautions are not adhered to, then the volume of air that fills the intravenous tubing from the drip chamber to the patient (25-30 mL in the pediatric infusion pump tubing used in our patient) can be infused by gravity into the patient's venous system. Because the consequences of VAE are so severe, the focus should be on prevention. Pumps used for home infusion therapy should have appropriate alarms to alert caregivers to the presence of air in the line. Obviously, this will not totally prevent this complication as this type of pump was used in our patient. It is crucial to educate caregivers of patients with central venous access regarding the hazards of VAE and safety measures to prevent it. With the increased use of home infusion therapy, ongoing evaluations of complications related to this form of therapy are mandatory so that there is continued evaluation of practices and appropriate changes made when necessary to increase further the safety of these techniques.

Cardiopulmonary Resuscitation↗

Expression of neuropeptides and growth-associated protein 43 (GAP-43) in cutaneous and mucosal nerve structures of the adult rat lower lip after mental nerve section.

The reinnervation of the adult rat lower lip has been investigated after unilateral section of the mental nerve. Rats were sacrificed at 4, 7, 9, 14, 30, and 90 days after the operation. A further group of animals with section of the mental nerve and block of the alveolar nerve regeneration, was sacrificed at 14 days. Specimens were processed for immunocytochemistry with antibodies against PGP 9.5, GAP-43 or neuropeptides (CGRP, SP and VIP). Four days after nerve section, axonal degeneration seems evident in the mental nerve branches and inside skin and mucosa. GAP-43 immunoreactivity is intense in the mental nerve 7 days after nerve section and it reaches its maximal expression and distribution in peripheral nerve fibres at 14 days. At 30 days, the decline in its expression is associated with the increase of PGP9.5-, SP-, and CGRP immunopositivity. VIP is observed only in perivascular fibres at all times observed. Present results suggest that, after sensory denervation of the rat lip, nerve fibres in skin and mucosa remain at lower density than normal. The different time courses in the expression of neuropeptides and GAP-43 suggest a possible early involvement of GAP-43 in peripheral nerve regeneration.

Animals↗

Lesion topography and outcome after thermocapsulotomy or gamma knife capsulotomy for obsessive-compulsive disorder: relevance of the right hemisphere.

OBJECTIVES: Obsessive-compulsive disorder is a common mental disorder, notorious for its chronicity and intractability. Stereotactic lesions within the anterior limb of the internal capsule have been shown to provide symptomatic relief in such refractory cases, but only few systematic evaluations have correlated anatomic lesion location with individual postoperative outcome. PATIENTS AND METHODS: Between 1976 and 1989, extremely disabled and otherwise intractable patients with a chronic deteriorating clinical course of obsessive-compulsive disorder underwent bilateral thermocapsulotomy (n = 22) or radiosurgical gamma knife capsulotomy (n = 13) at the Karolinska Hospital, Stockholm. Clinical morbidity was monitored prospectively pre- and postoperatively by using standardized psychiatric rating scales. In 29 patients (thermocapsulotomy, n = 19; gamma knife capsulotomy, n = 10), both psychiatric and magnetic resonance imaging follow-up data (median, 8.4 yr) were available. RESULTS: A right-sided anatomically defined lesion volume was identified in all successfully treated patients. This common topographic denominator was defined in the approximate middle of the anterior limb of the internal capsule on the plane parallel to the anterior commissure-posterior commissure line at the level of the foramen of Monro and 4 mm above on the plane defined by the internal cerebral vein. This region was unaffected in patients with poor outcomes. On the left side, no particular lesion topography was associated with clinical outcome. Topographic differences of lesion overlap between good and poor outcome groups were significant for the right side (Fisher's exact test, P < 0.005). CONCLUSION: The current anatomic long-term analysis after thermocapsulotomy or gamma knife capsulotomy for obsessive-compulsive disorder reveals common topographic features within the right-sided anterior limb of the internal capsule independent of treatment modality.

Adult↗

Primary intracranial arachnoidal cysts. A study of 67 childhood cases.

Sixty-seven cases (41 males and 26 females) of arachnoidal cysts in children under 11 years are reported. About 53% of cases were diagnosed before 1 year of life. Thirty-one (42.2%) were supratentorial (interhemispheric 9, temporal fossa 10, convexity 5, sylvian fissure 3, supra- and/or retrosellar 4); 31 (46.2%) infratentorial (supra- and/or retrocerebellar 22, foramen of Magendie 3, quadrigeminal cistern 5, pontocerebellar 1); 5 (7.5%) supra- and infratentorial. Macrocephaly was the presenting symptom in 48 cases (71.5%). Associated features were frequent: cranial asymmetry in 24; aqueductal stenosis in 10; agenesis of corpus callosum in 8; deficient cerebellar lobullation in 4; Chiari I malformation in 2; neurofibromatosis type 1 with dysgenetic zones of the brain in 1; arteriovenous malformation in 1. Diagnosis was made at autopsy in six cases in the days before computed tomography and magnetic resonance: three patients had a cyst in the supra- and retrocerebellar midline; two had a cyst in the quadrigeminal cistern and the sixth was a rare case with the cyst passing from the posterior fossa to the left lateral ventricle through a hole in the basal surface of the brain. Small and some middle-sized cysts were not treated. Big and some middle-sized cysts were usually treated by cysto- and/or ventriculoperitoneal shunts. Arachnoidal cysts of the quadrigeminal cistern usually present with aqueductal stenosis and have to be treated with ventriculoperitoneal shunt. Craniotomy and fenestration of the cysts were performed in some cases with good results. The average mental level of these children is usually moderately low.

Arachnoid Cysts↗

On the treatment of subependymal giant cell astrocytomas and associated hydrocephalus in tuberous sclerosis.

Between 1980 and 1992, 10 children affected by tuberous sclerosis and intraventricular subependymal giant cell astrocytomas were surgically treated at the Institute of Neurosurgery, Section of Pediatric Neurosurgery, Catholic University of Rome. Nine patients presented with signs and/or symptoms of intracranial hypertension; in all of them the neuroradiological investigations demonstrated the presence of a space-occupying lesion in the region of the foramen of Monro with secondary ventricular dilation. In the remaining patient, a 5-month-old male infant, an intraventricular mass was discovered by means of an ultrasound examination performed after the first epileptic fit. Three patients underwent a ventriculoperitoneal CSF shunt as first surgical procedure; in 2 of them it was subsequently necessary to remove the intraventricular tumor due to the frequent occlusion of the CSF shunt device. Seven subjects underwent the direct surgical excision of the lesion. In all of them the procedure resulted in the control of the associated hydrocephalus. On the basis of such an experience, the authors conclude that the surgical removal of the intraventricular tumors in patients with tuberous sclerosis and hydrocephalus is the most appropriate treatment. In fact, in the series considered here, the removal of the tumor was not accompanied by significant morbidity, and was followed by improvement in clinical conditions. In particular, in cases in whom the occurrence of hydrocephalus was associated with a worsening in the seizure disorder, the tumor removal and the correction of intracranial hypertension was followed by a significant reduction in frequency or even by the disappearance of the seizures. However, in no case presenting with mental impairment was a significant improvement observed in mental performances as a consequence of the surgical treatment.

Adolescent↗

Allometry in primates, with emphasis on scaling and the evolution of the brain.

Allometry should be defined broadly as the study of size and its consequences, not narrowly as the application of power functions to the data of growth. Variation in size may be ontogenetic, static or phyletic. Errors of omission and treatment have plagued the study of allometry in primates. Standard texts often treat brain size as an independent measure, ignoring its allometric relation with body size - on this basis, gracile australopithecines have been accorded the mental status of gorillas. Intrinsic allometries of the brain/body are likewise neglected: many authors cite cerebral folding as evidence of man's mental superiority, but folding is a mechanical correlate of brain size itself. Confusion among types of scaling heads errors of treatment in both historical primacy [Dubois' ontogenetic inferences from interspecific curves] and current frequency. The predicted parameters of brain-body plots differ greatly for ontogenetic, intrapopulational, interspecific and phyletic allometries. I then discuss basic trends in bivariate allometry at the ordinal level for internal organ weights, skeletal dimensions, lifespan and fetal weight. In considering the causes of basic bivariate allometries, I examine the reason for differences among types of scaling in brain-body relationships. The interspecific exponent of 0.66 strongly suggests a relationship to body surfaces, but we have no satisfactory explanation for why this should be so. The tripartite ontogenetic plot is a consequence of patterns in neuronal differentiation. We do not know why intraspecific exponents fall between 0.2 and 0.4; several partial explanations have been offered. Multivariate techniques have transcended the pictorial representation of transformed coordinates and offer new, powerful approaches to total allometric patterns. Allometry is most often used as a 'criterion for subtraction'. In order to assess the nature and purpose of an adaptation, we must be able to identify and isolate the aspect of its form that depends both upon its size and the size of the body within which it resides. Cranial indices and limb lengths are misinterpreted when authors apply no correction for body size. The search for a criterion of subtraction has been most diligently pursued in studies of the brain. Clearly, brain size must be assessed by comparison with a 'standard' animal of the same body size. But how shall size be measured, especially in fossils; and how shall a standard animal be construed. I discuss and criticize three methods recently used: RADINSKY'S foramen magnum criterion; Jerison's minimum convex polygons and cephalization quotients; and the indices of progression in comparison with 'basal' insectivores' of BAUCHOT, Stephan and their colleagues.

Animals↗