Bilateral Frontal Lesions Research Articles

Posterior reversible encephalopathy syndrome secondary to acute post-streptococcal glomerulonephritis in a child: a case report from the Tibetan plateau

BackgroundPosterior reversible encephalopathy syndrome (PRES) is a disorder of reversible vasogenic brain oedema with acute neurologic symptoms. It is a rare but serious disease that affects the central nervous system. PRES is a rare complication of acute post-streptococcal glomerulonephritis (APSGN). High altitude can accelerate vasogenic brain oedema by increasing cerebral blood flow (CBF), impairing cerebral autoregulation and promoting vascular inflammation. We report a case of PRES induced by acute post-streptococcal glomerulonephritis in a high-altitude environment.Case presentationA fourteen-year-old Tibetan girl presented with progressive headache with haematuria, facial swelling, dizziness and vomiting for 2 weeks as well as multiple episodes of tonic–clonic seizures for 14 h. She was diagnosed with APSGN based on laboratory tests and clinical symptoms. Brain magnetic resonance imaging (MRI) and computed tomography (CT) revealed bilateral frontal, parietal and occipital lesions that were compatible with the radiological diagnosis of PRES. The treatments included an antibiotic (penicillin), an antiepileptic drug, and hyperbaric oxygen (HBO) therapy. Follow-up MRI obtained 1 week after admission and CT obtained 4 weeks and 6 weeks after admission demonstrated complete resolution of the brain lesions.ConclusionsThe case illustrates a rare occurrence of PRES following APSGN in a 14-year-old child in the Tibetan Plateau. The hypoxic conditions of a high-altitude setting might lower the cerebral autoregulation threshold and amplify the endothelial inflammatory reaction, thus inducing PRES in patients with APSGN. It is important to recognize the clinical and radiologic features of PRES, and adjuvant HBO therapy can promote rapid recovery from this condition in high-altitude areas.

Truncal Instability and Titubation in Patients With Acute Encephalopathy With Reduced Subcortical Diffusion.

The present retrospective study aimed to investigate the presence of truncal instability or titubation after the first seizure and second phase in patients with acute encephalopathy with reduced subcortical diffusion (AED). Of the 15 patients with AED who were admitted to our hospital for 3 years and 2 months and had reached developmental milestones for sitting before disease onset, six experienced moderate-to-severe truncal instability while sitting after the first seizure. These patients had a significantly longer first seizure duration and significantly lower GCS scores 12–24 h after the first seizure, as well as significantly higher Tada score and Creatinine and blood glucose levels than those with mild or no truncal instability while in a seated position after the first seizure. Three 1-year-old children with bilateral frontal lobe lesions, particularly in the bilateral prefrontal lobe regions, demonstrated truncal titubation, which has not previously been reported as a clinical feature of AED. Tada score reported to be a predictor of AED prognosis and truncal instability in the sitting position after the first seizure may represent disease severity, but not the specific lesions. Conversely, truncal titubation might be suggestive of bilateral frontal lobe lesions, particularly in patients without severe instability. Further studies on the role of bilateral prefrontal lobe lesions to truncal titubation in patients with AED using more objective evaluation methods, such as stabilometry, are necessary.

Factors affecting cognition and emotion in patients with traumatic brain injury.

BACKGROUND:Cognitive and emotional disturbances are common serious issues in patients with traumatic brain injury (TBI). However, predictors associated with neuropsychological functions were not consistent.OBJECTIVE:To investigate factors affecting cognition and emotion in patients with TBI, we evaluated executive function, memory, and emotion based on injury severity and lesion location.METHODS:Neuropsychological outcomes of 80 TBI patients were evaluated via Wisconsin Card Sorting Test (WCST), Color Trail Test (CTT), Controlled Oral Word Association Test (COWAT), Everyday Memory Questionnaire (EMQ), Geriatric Depression Scale (GDS), State-Trait Anxiety Inventory (STAI), and Agitated Behavior Scale (ABS). WCST, CTT, and COWAT assessed executive function; EMQ assessed everyday memory; and GDS, STAI, and ABS assessed emotion. Patients were categorized according to lateralization of lesion and existence of frontal lobe injury.RESULTS:Patients with longer duration of loss of consciousness (LOC) showed more severe deficits in everyday memory and agitated behaviors. The frontal lesion group showed poorer performance in executive function and higher agitation than the non-frontal lesion group. Patients with bilateral frontal lesion showed greater deficits in executive function and were more depressed than unilateral frontal lesion groups. Especially in those unilateral frontal lesion groups, right side frontal lesion group was worse on executive function than left side frontal lesion group.CONCLUSIONS:Duration of LOC and lesion location are main parameters affecting executive function, everyday memory, and emotion in neuropsychological outcomes following TBI, suggesting that these parameters need to be considered for cognitive rehabilitation interventions.

A strange oculomotor palsy with eosinophilia

A 75-year-old man was admitted to the Department of internal medicine because of a 2-month history of neurological deterioration. During the previous year, he complained of recurrent sinusitis, asthma, arthralgias, myalgias and asthenia. Later on, an oculomotor palsy, weakness and disturbance of the sensibility of the right upper limb appeared. Blood sample showed 6510 eosinophils per microlitre. The cerebral magnetic resonance demonstrated bilateral frontal and left parietal subcortical lesions from which the most voluminous presented large haemorrhagic areas. A cerebral biopsy showed small vessel’s vasculitis, fibrinoid necrosis and extravascular eosinophilic encroachment. A diagnosis of oculomotor palsy secondary to eosinophilic granulomatosis with polyangeitis was then made, which was successfully treated with corticosteroids and cyclophosphamide.

A case of hospital-acquired GNB infection - P. aeruginosa meningoencephalitis post laparoscopic cholecystectomy for biliary pancreatitis, complicated with portal vein branch thrombosis and intracerebral ischemic and hemorrhagic lesions

Case report We present the case of a female patient admitted to our clinic with a suspicion of acute bacterial meningoencephalitis, one month after a laparoscopic cholecystectomy. During the first 48 hours she presented generalized seizures, 5-6 daily, with a duration that ranged from 30 to 60 seconds, that responded to medical therapy. The CSF cultures and the pulmonary tract secretions both tested positive for P. aeruginosa. The antibiotic regimen consisted of iv meropenem, colistin and ciprofloxacin for 7 days, then meropenem and ciprofloxacin for 21 days. The evolution and the treatment decisions were complicated by the discovery on the cerebral MRI of bilateral frontal ischemic and hemorrhagic lesions and a portal vein branch thrombosis. The patient registered almost complete cognitive and motor recovery, and is continuing the kinetotherapy.

P17.72 * ACUTE LYMPHOBLASTIC LEUKEMIA AFTER TEMOZOLOMIDE TREATMENT FOR OLIGODENDROGLIOMA: CASE REPORT

INTRODUCTION: Temozolomide is an alkylating agent used in the treatment of high grade gliomas. The drug acts blocking cell division so tumor growth is slowed. TMZ has been reported to cause secondary myelodysplastic syndrome and acute myeloid leukemia while TMZ related acute lymphoblastic leukemia (ALL) is rare. We describe a man affected by a oligodendroglioma, who developed a T-cell acute lymphoblastic leukemia 12 months after stopping TMZ. CASE REPORT: A 41-years-old male presented a new-onset generalized seizure. A CT brain scan showed a bilateral frontal lesion and calcifications within. MRI documented a small contrast-enhancement in the left frontal region. The patient underwent surgical treatment. Histological examination revealed a oligodendroglioma (WHO grade II, 13% proliferation index). The molecular study identified a 1p/19q codeletion. The patient was treated with adiuvant chemotherapy (TMZ 200 mg/m2/day for 5 days in a 28- day-cycle). He was given a total of 36 cycles, ended in October 2012. Antiepileptic therapy was associated, then stopped after about three years, because he was seizures-free. During the three years of chemotherapy the disease remain stable. In conjunction with the 36th cycle the MRI perfusion and spettroscopy demonstrated a small tumor's recurrence in the left frontal region that was treated with gamma-knife radio surgery (total dose 20 Gy). The procedure was well tolerated and after three months the brain MRI was improved. The following neuroradiological examinations showed a stable disease. 12 months from the last TMZ-cycle submandibular and inguinal lymphadenopathy were discovered and the presence of a small ulcerated lesion with blood contours in the left peritonsillar side was observed. The patient underwent to Haematologist and after additional blood tests, T-cell acute lymphoblastic leukemia was diagnosed. The immunocytometric analysis on bone marrow cells showed the following phenotype: CD7++; CD8++, CD10 high, TdT++, CD38++. Cytogenetics analysis resulted in a normal karyotype. CT thoracic-abdominal scan showed diffuse lymphoadenophaties. The patients was treated with the protocol for lymphoblastic leukaemia running in out institution, with idarubicin, vincristine, cyclophosphamide, l-asparaginase and steroids. He obtained complete remission and he is now under treatment with cycles of consolidation chemotherapy. CONCLUSION: This is the first case described of T-cell acute lymphoblastic leukemia following TMZ therapy. TMZ is largely used for treatment of gliomas. The possibility that a therapy-related leukemia may develop must be taken in account in patients with haematological signs. Although the phenotype of this T-cell leukaemia is different from the other reported cases (until now only B-cell), the temporal relation between TMZ therapy and the diagnosis of leukaemia strongly suggests the causality between these two events.

Carotid Artery Free-Floating Thrombus Caused by Paradoxical Embolization From Greater Saphenous Vein Ascending Thrombophlebitis

Stroke of unknown origin in young patients is seen to be closely correlated with patent foramen ovale (PFO) than stroke in patients with established stroke mechanisms. We report a case of a young woman without cardiovascular risk factors who was admitted to our emergency department with listlessness and altered mental status. The clinical examination revealed right lower limb swelling. Magnetic resonance imaging and contrast-enhanced computed tomographic scans revealed a free floating thrombus of the left internal carotid artery (ICA) with a large bilateral frontal ischemic lesion. The diagnosis of a medium-sized PFO with moderate right-to-left contrast shunting was made after transesophageal echocardiography. No other cardiac sources for embolization were detected, while an ascending thrombophlebitis of the right greater saphenous vein was detected by venous Doppler ultrasonography. These findings support the diagnosis of ICA free-floating thrombus caused by paradoxical embolization (via the PFO) of clot from the greater saphenous vein. The patient underwent emergency saphenofemoral disconnection with femoral vein thrombectomy and subsequently carotid artery thrombectomy under general anesthesia. No carotid atheromatous wall lesions were detected at surgical exploration; no immunologic pathology, hypercoagulable status, or malignancy were recorded. No hemorrhagic cerebral complications were observed in the postoperative period, and the patient had an improvement of her neurologic status (a reduction of the National Institutes of Health Stroke Scale score from 7 to 3). Her recovery was uneventful. The patient was transferred for rehabilitation on postoperative day 5 with oral anticoagulation. Six-month ultrasound follow-up revealed deep and superficial venous system and carotid artery patency. The patient was asymptomatic and anticoagulation was discontinued. Paradoxical cerebral embolization through a PFO is a rare phenomenon that, in our patient, appeared to have resulted in stroke caused by a free-floating thrombus in the ICA. Accurate evaluation of carotid and lower limb veins by duplex scan is mandatory in cases of stroke of unknown origin, and urgent surgical repair can be useful in order to improve the clinical outcome.

Acute Infantile Encephalopathy Predominantly Affecting the Frontal Lobes (AIEF)

Acute Infantile Encephalopathy Predominantly Affecting the Frontal Lobes (AIEF) is a relatively recent described entity. This article includes case reports of two patients who had bifrontal involvement during acute febrile encephalopathy. Case 1 describes a 1-y-old boy who presented with hyperpyrexia and dialeptic seizures. Imaging revealed significant bilateral frontal lobe involvement while serology proved presence of Influenza B infection. Over a period of onewk, he recovered with significant cognitive decline and perseveratory behavior. Another 6-y-old boy presented with language and behavioral problems suggestive of frontal dysfunction after recovering from prolonged impairment of consciousness following a convulsive status epilepticus. Bilateral superior frontal lesions with gyral swelling was evident on neuroimaging. These cases are among the very few cases of AIEF described in recent literature and the article also reviews this unique subtype of acute encephalopathy.

Isolated gait apraxia from an acute unilateral parasagittal lesion

Gait apraxia (GA) is defined by the inability to activate and mainain ambulation from deficits that are not attributable to motor, ensory, cerebellar, or psychiatric disease [1]. In GA, particular difculty is seen with initiating locomotion and turning [1]. Lesional A has mainly been reported in bilateral medial frontal lesions 1,2]. Unilateral lesions causing isolated GA, also predominantly in rontal cortex, have rarely been demonstrated in the magnetic resnance imaging (MRI) era, and usually present in a chronic and rogressive fashion [1,2]. We report a patient experiencing sudden nset isolated GA, providing unique insights into its clinical and euroanatomical correlates.

Apresentando um instrumento de avaliação da comunicação à Fonoaudiologia Brasileira: Bateria MAC

an assessment instrument to evaluate communication impairment after right brain damage: the Montreal Communication Evaluation Battery, an adapted brazilian version of the original canadian instrument--Protocole Montréal d'Evaluation de la Communication. Instruments that evaluate discursive, pragmatic, lexical-semantic and prosodic impairments are important for the diagnosis of communication disorders which are present in approximately 50% of the individuals with right brain damage. Systematic studies of the communication profile after lesions on this side of the brain have been carried out only during the last two decades. to present the Montreal Communication Evaluation Battery to brazilian speech therapists. the described instrument is an useful tool in the clinic for assessing four processes related to the communicative and linguistic abilities: discursive, pragmatic-inferential, lexical-semantic and prosodic components. It is has been normalized, validated and its reliability has been confirmed. Although this instrument was developed and adapted for diagnosing communication disorders in individuals with right brain damage people, it can also be helpful in investigating communication sequels in traumatic brain injury, dementia, bilateral frontal lesions, left-brain damage, psychopathologies, such as schizophrenia, among others.

Behavioral and hormonal reactivity to threat: Effects of selective amygdala, hippocampal or orbital frontal lesions in monkeys

We compared the effects of bilateral amygdala, hippocampal or orbital frontal cortex lesions on emotional and hormonal reactivity in rhesus monkeys (Macaca mulatta). Experiment 1 measured behavioral reactivity to an unfamiliar human intruder before and after surgery. Animals with amygdala lesions demonstrated decreases in one passive defensive behavior (freezing), whereas animals with hippocampal lesions showed decreases in a more stimulus-directed defensive behavior (tooth grinding). Orbital frontal cortex lesions also reduced these two defensive behaviors, as well as decreased cage-shaking dominance displays. Animals with amygdala, hippocampal or sham lesions also demonstrated increased tension-related behaviors after surgery, but those with orbital frontal lesions did not. Finally, all three lesions diminished the operated animals' ability to modulate tension-related behaviors depending on the magnitude of threat posed by the human intruder. Experiment 2 measured circulating levels of cortisol and testosterone when a subset of these same animals was at rest and following physical restraint, temporary isolation, exposure to threatening objects and social interactions with an unfamiliar conspecific. None of the lesions impacted on testosterone levels in any condition. Amygdala or orbital frontal lesions blunted cortisol reactivity during isolation from peers, but not during any other condition. Hippocampal lesions did not alter circulating levels of cortisol under any condition. These results indicate that the amygdala, hippocampus and orbital frontal cortex play distinct, yet complimentary roles in coordinating emotional and hormonal reactivity to threat.

Object utilization and object usage: A single-case study

ABSTRACT It has been suggested that both conceptual knowledge and the ability to infer function from structure can support object use. By contrast, we propose that object use requires solely the ability to reason about technical ends. Technical ends (e.g., cutting) are not purposes (e.g., eating), but the technical way to achieve them. This perspective suggests that there is no mutual relationship between technical ends and purposes since the same purpose (e.g., writing) can be achieved thanks to distinct technical ends (graving, tracing), and, inversely, the same technical end (e.g., tracing) can achieve different purposes (making up, writing). Thus, conceptual knowledge might determine which technical end is usually associated with a given purpose. To contribute to the discussion, we described the behaviour of a female patient with left temporal lobe lesions and bilateral frontal lobe lesions following a closed-head injury. Conceptual knowledge was impaired. She encountered difficulties in demonstrating the use of objects in isolation (e.g., using a screwdriver without the screw). The presence of a recipient (e.g., using a screwdriver with the screw) improved her performance. The performance was also normal when asked to perform unusual applications of objects to achieve a goal for which the usually applied object was not provided (e.g., screwing a screw with a knife). Consistent with the theoretical framework supported here, her performance profile suggests an intact ability to reason about technical ends (i.e., utilization), in the presence of a defective ability to determine the usual relationship between technical ends and purposes (i.e., usage).

Neuroanatomy of pseudobulbar affect

Pseudobulbar affect (PBA) is defined as episodes of involuntary crying, laughing, or both in the absence of a matching subjective mood state. This neuropsychiatric syndrome can be found in a number of neurological disorders including multiple sclerosis (MS). The aim of this study was to identify neuroanatomical correlates of PBA in multiple sclerosis (MS) using a case-control 1.5T MRI study. MS patients with (n = 14) and without (n = 14) PBA were matched on demographic, disease course, and disability variables. Comorbid psychiatric disorders including depressive and anxiety disorders were absent. Hypo- and hyperintense lesion volumes plus measurements of atrophy were obtained and localized anatomically according to parcellated brain regions. Between-group statistical comparisons were undertaken with alpha set at 0.01 for the primary analysis. Discrete differences in lesion volume were noted in six regions: Brainstem hypointense lesions, bilateral inferior parietal and medial inferior frontal hyperintense lesions, and right medial superior frontal hyperintense lesions were all significantly higher in the PBA group. A logistic regression model identified four of these variables (brainstem hypointense, left inferior parietal hyperintense, and left and right medial inferior frontal hyperintense lesion volumes) that accounted for 70% of the variance when it came to explaining the presence of PBA. In conclusion, MS patients with PBA have a distinct distribution of brain lesions when compared to a matched MS sample without PBA. The lesion data support a widely-dispersed neural network involving frontal, parietal, and brainstem regions in the pathophysiology of PBA.

Measuring reward assessment in a semi-naturalistic context: The effects of selective amygdala, orbital frontal or hippocampal lesions

Studying the neural mechanisms underlying complex goal-directed behaviors, such as social behavior, reward seeking or punishment avoidance, has become increasingly tractable in humans, nonhuman primates and rodents. In most experiments, however, goal-directed behaviors are measured in a laboratory setting, which is vastly different from the context in which these behaviors naturally occur. This study adapted a reward assessment paradigm, previously conducted with rhesus monkeys (Macaca mulatta) in the controlled environment of a Wisconsin General Testing Apparatus (WGTA) [Machado CJ, Bachevalier J (2007) The effects of selective amygdala, orbital frontal cortex or hippocampal formation lesions on reward assessment in nonhuman primates. Eur J Neurosci 25:2885–2904], to a more naturalistic context. We used this new paradigm to examine the effects of bilateral amygdaloid, hippocampal or orbital frontal cortex lesions on established food and nonfood preferences. Behavioral modification following reinforcer devaluation was also measured. Consistent with our previous study, none of the lesions produced changes in preference for palatable foods relative to pre-surgery, but animals with amygdala lesions displayed heightened preference for unpalatable foods that control or other operated animals typically avoided. In contrast to several previous WGTA-based experiments, nonfood preference was not affected by any of the lesions. Finally, animals with orbital frontal cortex lesions continued to select preferred foods after satiation, but those with amygdala, hippocampal or sham lesions altered their foraging behavior appropriately and selected less of the sated food. These findings parallel food devaluation results obtained with these same animals when tested in the WGTA. Overall, this study stresses the importance of testing context when measuring decision-making abilities in nonhuman primates with selective brain lesions.

The effects of selective amygdala, orbital frontal cortex or hippocampal formation lesions on reward assessment in nonhuman primates

We examined the effects of bilateral amygdaloid, hippocampal or orbital frontal cortex lesions on reward assessment in rhesus monkeys (Macaca mulatta). In Experiment 1, basic preferences for foods and inedible nonfoods were measured pre- and postsurgery. None of the lesions produced changes in animals' preferences for palatable foods or raw meat relative to presurgery, although amygdaloid or hippocampal lesions yielded increased preference for inedible nonfoods postsurgery. When the reinforcement value of each animal's highest-preferred food was decreased by selective satiation, only animals with neurotoxic orbital frontal cortex lesions continued to select the sated food. Experiment 2 measured the impact of each lesion on learning 60 concurrent discrimination problems and, then, on flexibly avoiding objects associated with sated foods in favour of objects associated with nonsated foods. None of the lesions affected concurrent discrimination learning, but animals with neurotoxic amygdala or aspiration orbital frontal lesions could not refrain from displacing items covering devalued foods. Only animals with orbital lesions also selected the devalued food beneath the object. The results indicate a functional dissociation for the amygdala and orbital frontal cortex in reward assessment, depending on the type of the reinforcer available (objects vs. food). Finally, this is the first study indicating that the hippocampal formation is involved in the assessment of familiar nonfoods, but not in judging the current value of unconditioned and conditioned reinforcers.

Character changes from idiopathic cranial pachymeningoencephalitis

A 66-year-old man with idiopathic cranial pachymeningoencephalitis was described. He suffered from left orbital pain, and character changes. He became short tempered, and was very attached to trifles. Two years prior to these symptoms, he had developed transient left abducent nerve palsy. Head MRI showed a thickening and enhancement of the dura mater on gadolinium-enhanced T1-weighted images, and high signal intensity lesions at bilateral frontal lobes predominantly in the white matter on T2-weighted images. Biopsies revealed microglial proliferation in the cerebral parenchyma, and mild lymphocytic perivascular infiltration. No evidence of intracranial infection was detected. We therefore treated him with methylprednisolone pulse therapy followed by oral prednisolone. His character became gradually normalized, and bilateral frontal lobe lesions seen on MRI disappeared. This is the first case to describe recurrent pachymeningoencephalitis with character changes, and symptoms were probably due to frontal lobe dysfunction.

Un ptosis palpébral révélateur d'une bilharziose du tronc cérébral

To describe published cases of cerebral mansoni schistosomiasis and three others and discuss the diagnosis and treatment of cerebral pseudotumoral schistosomiasis.In case 1, a 20-year-old man presented with occipital headache, intense dizziness, visual alterations, nausea, decreased appetite, and asthenia. Cranial computed tomography (CT) revealed an expansive cerebellar lesion in the right hemisphere with no contrast enhancement. The patient had complete resection of the lesion. Anatomicopathological examination revealed a schistosomal granuloma. In case 2, a 22-year-old man presented with generalized tonic-clonic seizure. Cranial CT and magnetic resonance imaging (MRI) revealed an expansive bilateral middle frontal lesion, with contrast uptake close to the cingulate gyrus and corpus callosum. The patient underwent left frontal craniotomy, and an interhemispheric approach was used to resect part of the lesion. In case 3, a 32-year-old man presented with generalized tonic-clonic seizures. Cranial CT showed a hyperdense intense intracranial expansive lesion that presented contrast uptake in the left temporal region. The patient had complete resection of the lesion.A surgical approach with lesion resection or stereotaxic biopsy is warranted to determine the diagnosis definitively. Antiparasitic drugs must be administered to complete treatment.

A Case of Amnesia at an Early Age

A dissociation between short- and long-term memory (LTM) and between the episodic and the semantic component of LTM is reported in a young girl who became amnesic at the age of 6 after an episode of acute encephalopathy resulting in bilateral frontal, insular, thalamic, ponto-mesencephalic, hippocampal and temporal lesions, as documented by MRI. The girl became amnesic a few months after starting school. A follow-up investigation showed that she was able to learn to read, write and acquire number facts and procedures and to improve her semantic knowledge. Our results show that the features of adult amnesia can also be found in children and that new semantic knowledge can be acquired in spite of an anterograde memory deficit. This dissociation does not agree with theories viewing long- term declarative memory as a unitary process mediated by the hippocampal system, but supports recent hypotheses that the acquisition of semantic knowledge is independent from episodic memory processes, and takes place through spared cortical regions subjacent to the hippocampi (Vargha-Khadem et al., 1997).

Effects of left frontal lesions on the selection of context-appropriate meanings.

The present study examined the role of the left frontal cortex in strategic aspects of semantic processing. Participants were tested in a semantic priming task involving the meaning access of ambiguous and unambiguous words. Patients with left or bilateral frontal lesions failed to develop semantic facilitation of context-appropriate homograph meanings relative to age-matched controls and patients with right frontal lesions who produced more facilitation than controls. When the ambiguous words, however, were replaced by unambiguous words, patients with left frontal lesions improved to normal levels of semantic priming. This pattern of results seems difficult to explain in terms of a problem to access semantic information per se or to use contextual cues. The findings are, however, consistent with a deficit in selecting context-appropriate meanings in the presence of competing meanings.

Effects of left frontal lesions on the selection of context-appropriate meanings.

The present study examined the role of the left frontal cortex in strategic aspects of semantic processing. Participants were tested in a semantic priming task involving the meaning access of ambiguous and unambiguous words. Patients with left or bilateral frontal lesions failed to develop semantic facilitation of context-appropriate homograph meanings relative to age-matched controls and patients with right frontal lesions who produced more facilitation than controls. When the ambiguous words, however, were replaced by unambiguous words, patients with left frontal lesions improved to normal levels of semantic priming. This pattern of results seems difficult to explain in terms of a problem to access semantic information per se or to use contextual cues. The findings are, however, consistent with a deficit in selecting context-appropriate meanings in the presence of competing meanings.