Thread: Neurology Clinical Cases

Midbrain Lesion - VASCULAR LESIONS - TEGMENTUM OF THE MIDBRAIN (BENEDICKT'S SYNDROME)

A Sample Case: An usually alert 80 year old man was observed to have an episode of loss of consciousness. Upon awakening he complained of double vision and there was a notable tremor in his left arm.

The general physical exam was normal for a man his age. There was a mildly elevated blood pressure. Mental status was good and speech was articulate and appropriate.

With the eyelids retracted the right eye had a dilated pupil and a lateral strabismus. On attempted lateral gaze to the left the right eye would not proceed across the midline. Although vision was normal the right pupil did not constrict in either the direct or consensual pupillary light reflexes. Hearing was normal as were cranial nerves 5 through 12. Pain and temperature sensation from the face and body was normal bilaterally. Proprioception and vibratory sense on the right side of the body was normal but was diminished on the left.

Muscle strength on the left was slightly diminished and deep tendon reflexes were slightly increased. There was no Babinski sign. The finger-to-nose test was normal on the right but the left arm showed an intention tremor and dysmetria. There were occasional involuntary movements of the left arm.


Explanation -

Sudden momentary loss of consciousness is generally due to a transient ischemia but in this patient there are residual signs as well. In the right eye, 3rd nerve injury is indicated by lateral strabismus, inability to adduct on attempted lateral gaze, dilated pupil, and loss of pupillary constriction. Other cranial nerves showed no signs of involvement.

Diminished proprioception and vibratory sense on the left side of the body indicates a tegmental injury of the right medial lemniscus but without involvement of nearby spinothalamic tracts since pain and temperature sensation were normal.

There were incoordinate movements and intention tremor consistent with a cerebellar ataxia. Usually we associate left sided cerebellar signs with injury to the left cerebellar hemisphere; here injury on the right side of the midbrain has injured the cerebellothalamic fibers after they crossed from the left side. Involuntary movements are usually associated with injury to the basal ganglia and/or its associated nuclei, in this case the substantia nigra. Lesions to the right basal ganglia apparatus produce signs contralaterally through the corticospinal tract. Here, motor findings also included mild weakness and hyperreflexia on the left involving the corticospinal tract on the right side

The major indicators of Benedikt's syndrome are injury to the 3rd nerve and contralateral involvement of the cerebellothalamic fibers. Near the dentatothalamic fibers are the fibers of the medial lemniscus. Pressure from such a lesion can involve the nearby substantia nigra and sometimes the corticospinal tract. The blood supply to this area is from the distal portions of the lateral and paramedian branches of the basilar and posterior cerebral arteries.

Midbrain Lesion - NEOPLASMS- DORSAL MIDBRAIN SYNDROME (PARINAUD'S SYNDROME)

A Sample Case: A 6 year old boy was noticed by his mother to have developed pubic hair and an enlarged penis.

The neurologic examination revealed a bilateral paralysis of upward gaze and a questionable weakness of convergence. The pupils constricted upon convergence but not in response to light.


Explanation -

When due to a tumor of the pineal gland this syndrome may be marked by precocious puberty primarily occurring in males; the tumor secretes hCG (human chorionic gonadotrphic hormone) which causes testosterone production.

The neurologic manifestation of this syndrome is primarily the inability to move the eyes vertically upward but is not invariably associated with paralysis of downward gaze. The lesion occurs in the dorsal part of the superior colliculus and so is associated with the region of oculomotor nuclei, pretectal nuclei,. posterior commissure, and the vertical gaze center associated with the rostral MLF. There may be changes in pupillary responses (fixed pupils in response to light but which constrict in accommodation) and often there is eyelid retraction and a lag in elevating the lid. Often there is no evidence of paralysis of individual ocular muscles.

This syndrome occurs with injury to the superior colliculus, pretectal area, and posterior commissure. It occurs in encephalitis, and in tumors of the pineal gland, posterior 3rd ventricle, and midbrain. A vascular etiology is occlusion of the collicular branches of the posterior choroidal artery which is a branch of the posterior cerebral artery.

Diencephalon Lesion - VASCULAR LESIONS - THALAMIC SYNDROME

A Sample Case: A 60 year old man was noticed by his son as suddenly acting confused and having slurred speech.

The patient's history included high blood pressure which was confirmed upon examination. Otherwise he was in generally good health. There was no papilledema.

The neurologic exam indicated disorientation with respect to time, place and personal details. He had poor memory of recent events. He confused the right and left sides of his body and perseverated his poorly articulated speech which included many inappropriate words.

Ocular movements were all intact but he had a right homonymous hemianopsia. Pupils were symmetric and normally responsive to light. Hearing was normal. Corneal, gag, uvula and jaw-jerk reflexes were normal. The tongue behaved and appeared normal. When asked to smile his facial muscles responded symmetrically; when smiling in response to a joke only the left side smiled.

There was marked weakness of the right arm and leg with increased deep tendon reflexes and a Babinski sign. Pain and temperature sensation were normal on the right side but discriminitive touch and proprioception were reduced.


Explanation -

Disorientation, confusion and impaired speech indicates a problem at diencephalic or cortical levels. The right visual field defect indicates a lesion behind the chiasm on the left, e.g., optic tract, lateral geniculate, optic radiation or visual cortex. Volitional facial motor response was normal but the loss of full emotional smiling also indicates a lesion above the 7th nucleus; the basal ganglia participates with the frontal cortex and thalamus in emotional expression - a lesion on the left would result in a deficit on the right. Other cranial nerve functions are normal.

Upper motor neuron signs of the right arm and leg indicate a corticospinal tract injury on the left - perhaps in the internal capsule or above. Motor cortex injury would require a very large injury along the lateral aspect of the precentral gyrus and would probably have spared the foot which is represented on the medial side. A lesion in the posterior limb of the internal capsule would give the described loss of motor function. The homonymous hemianopsia is consistent with a focal lesion of the internal capsule lesion, otherwise a multifocal lesion is required to explain findings which include the frontal motor cortex and the occipital visual cortex. (A vascular lesion of the visual cortex is likely to result in a quadrantic defect and/or macular sparing.) Sensory findings where pain and temperature sensation on the right were normal but proprioception was not, is not readily explained by an internal capsule lesion but rather suggests a lesion of the nearby medial lemniscus on the left.

The sudden onset suggests a vascular lesion involving the thalamus and posterior limb of the internal capsule including optic radiations. The blood supply to the thalamus comes from penetrating branches of the circle of Willis, basilar, posterior cerebral and middle cerebral arteries.

Diencephalon Lesion - VASCULAR LESIONS - THALAMIC PAIN SYNDROME (of DEJERINE-ROUSSY)

A Sample Case: A progressive numbness of his arm and left leg, which over time resolved, next proceeded to great discomfort and led a man of 40 years of age to seek medical assistance. He had already noticed a mild weakness on his left side.

The patient was alert and well oriented with good long-term memory but less good short-term memory functions. His general physical exam was normal. Proprioception and postural sensibility were reduced on the left. Application of a painful stimulus elicited a stabbing, knife-like or burning, agonizing sensation; even light touch such as the pressure of clothing was extremely uncomfortable. The face showed no sensory alterations. The discomfort was not relieved by analgesics.

A left-sided spastic hemiparesis was found and there were involuntary choreiform movements noted. Voluntary movements of the facial muscles were normal on both sides but emotional responses were asymmetric due to lack of involvement of the left side of the face.

Eye movements were normal but visual field examination showed a left homonymous lower quadranopsia. Hearing was normal. Jaw jerk and corneal reflexes were normal. Tongue and palate responses were normal.


Explanation -

The unusual facet of this case, which makes it recognizable, is the description of the pain. The agonizing pain on the left ("stabbing, crushing, burning, etc") is actually a dysthesia resulting from irritation of the thalamus (on the right side), which can be brought about by the most trivial of cutaneous stimuli. The thalamic nucleus most often involved is the ventroposterolateral nucleus (and results in the loss of proprioception). Even changes in ambient temperature, barometric pressure, music, fright, or argument can aggravate the pain. Often the syndrome begins with numbness, which may spare the face, but then evolves into the entire painful syndrome. The involvement of the arms, trunk and legs argues against a cortical lesion.

Spastic hemiparesis of the left arm and leg suggests injury to the right corticospinal tract, probably in the posterior limb of the internal capsule, which lies just lateral to the thalamus and may be injured directly or by swelling of the affected thalamus. The involuntary choreoathetoid movements could also result from the nearby ventrolateral nucleus of the thalamus or subthalamic nucleus containing efferents of the basal ganglia. This injury to the basal ganglia, its efferent pathways, or the related thalamic nuclei, result in loss of emotional facial responses.

General cortical functions are preserved but there is a deficit in short-term memory which may require a relay in the thalamus prior to its registration.

There is no cranial nerve involvement except for the optic nerve where there is a left lower quadrantic anopsia which indicates a post-chiasmatic lesion on the right. Only the lower visual field is missing so the medial portion of the lateral geniculate nucleus, the upper fibers of the optic radiation, or the cuneus of the visual cortex in the occipital lobe may be considered. The smallest lesion likely would be in the posterior thalamus and would exclude the visual cortex.

The lesion appears to be unilateral and localized to the posterior portion of the thalamus. If the lesion is due to a vascular occlusion then the vessels involved would be the thalamogeniculate branches from the proximal portion of the posterior cerebral artery.

Diencephalon Lesion - NEOPLASMS - HYPOTHALAMUS - CRANIOPHARYNGIOMA

A Sample Case: A child of 6 complained of headache and was vomiting. The mother described the child as constantly urinating. Neurologic examination showed mild papilledema and increased intracranial pressure but otherwise most of the neurologic examination, motor and sensory, was normal. Examination of the visual fields however revealed a bitemporal hemianopsia. X-ray studies revealed a midline, suprasellar, calcifying tumor.


Explanation -

Bitemporal hemianopsia is usually due to midline pressure on the optic chiasm. Headache, vomiting and papilledema are often due to increased intracranial pressure which may accompany space-taking lesions. Frequent urination may signal a decrease in antidiuretic hormone which is made in the supraoptic and paraventricular nuclei of the anterior hypothalamus. (It may also indicate a lesion of the posterior lobe of the pituitary.)

Craniopharyngiomas arise from the ectodermal remnants of Rathke's pouch. Most hypothalamic tumors occur in the midline and hence when they present with visual symptoms they impact the crossing fibers in the optic chiasm.

Diencephalon Lesion - NEOPLASMS - HYPOTHALAMUS - GLIOMA

A Sample Case: Admitted to the hospital complaining of chest pain, a 50 year old man also complained of problems with vision which were getting progressively worse. He described drinking copious amounts of water each day for many years. This was accompanied by polyuria and nocturia. Upon questioning he revealed that he had not ever had a significant sex drive.

His general physical examination was consistent with an acute myocardial infarct. He weighed 250 pounds and was 5 feet 6 inches tall. Apart from cardiac abnormalities he was in generally good health.

He was alert, well oriented with good memory, and appropriate well articulated speech. Cranial nerve examination was normal except for vision which showed a bitemporal hemianopsia. Motor and sensory examination were normal. During his hospital stay his temperature fluctuated between 37.30 and 37.90 C daily.


Explanation -

There was no indication of problems with higher cortical functions. Sensory and motor signs were absent as were cranial nerve signs except for the optic nerves. The bitemporal hemianopsia indicates involvement with the optic chiasm.

Long-standing excessive intake of water suggests diabetes insipidus which may be due to lesions of the hypothalamus or the posterior pituitary for the synthesis and release of antidiuretic hormone (ADH). Additionally, he had poor temperature control, was of short stature, overweight, and with self-described low libido. These phenomena are functions controlled by the hypothalamus. In the midline of the hypothalamus is the ventromedial nucleus which controls food intake, and the supraoptic/paraventricular nuclei which synthesize ADH; the hypothalamus is known to regulate body temperature and secrete gonadotrophin releasing-hormone, which may be responsible for the absence of libido. The long standing, slowly progressive nature of these problems suggest that the etiology is not of vascular origin but more likely is due to a slow growing tumor.

Cerebellum Lesion - VASCULAR LESIONS - OCCLUSION OF THE SUPERIOR CEREBELLAR ARTERY

A Sample Case: A 50 year old man had headache and vomiting. As he walked he staggered; his gait was broad-based and he drifted to the left. His mental status was normal but the cranial nerve exam showed a nystagmus to the left on attempted horizontal gaze to the left. All volitional eye movements were normal but the left pupil was smaller than the right though both responded normally to light. The left palpebral fissure was narrower than the right. Sensation on the face was normal as was the corneal reflex. The muscles of the lower face and the muscles of mastication were weaker on the right. He had intention tremor of the left arm and leg. Two-point discrimination on the body was normal but pain and temperature sensation was reduced from the right arm and legs.


Explanation -

The sudden onset of symptoms such as staggering gait suggests a vascular lesion. Though there is headache and vomiting, the patient's mental status suggests that the cerebral hemispheres are unaffected. The nystagmus upon gaze to the left suggests a lesion of the vestibular system or a left cerebellar involvement. The patient's left eyelid drooped and the pupil was constricted as in a Horner's syndrome where the descending autonomics (sympathetic innervation) are compromised. Weakness of the lower facial muscles and muscles of mastication on the right indicates impairment of the upper motor neurons on the left to the motor nuclei of the 5th and 7th cranial nerves. This helps localize the level of this lesion to above the mid-pons.

The strength and deep tendon reflexes of both arms and legs were noted to be generally normal yet there was weakness of the left arm as indicated by pronator drift. The unsteady gait and ataxia on the left are signs of left cerebellar hemisphere disease or the superior cerebellar peduncle from the left.

Diminished sensation on the right side of the body indicates involvement of the spinothalamic tracts on the left, located in the reticular formation near descending autonomic fibers.

The signs of cerebellar ataxia might indicate of involvement of several vessels supplying the cerebellum. The superior cerebellar artery wraps around the cerebral peduncle of the midbrain arching backwards to the superior surface of the cerebellum. In its passage to the cerebellum it crosses over the superior cerebellar peduncle, which it supplies along with the lateral tegmentum of the upper pons, the site of the lesion, wherein lie the spinothalamic tracts, the descending autonomics and, presumably, the upper motor neurons to the facial and trigeminal motor nuclei.

Cerebellum Lesion - NEOPLASMS - TUMOR OF THE CEREBELLAR HEMISPHERE

A Sample Case: A 45 year old woman developed headaches and vomiting in the past month. The headaches awakened her from sleep. She had been stumbling as she walked and often staggered to her right side.

The neurological exam indicated that mental status was normal but bilateral papilledema was present. Pupils were of normal size and fully reactive to light. On attempted lateral gaze to the right a horizontal nystagmus was seen. There were full and symmetric ocular movements and no double vision. Cranial nerve examination was normal.

Muscle strength was nearly normal; deep tendon responses and muscle tone were reduced on the right. Gait was widebased and upon walking she tended to veer toward the right. She demonstrated a positive Romberg sign when standing with the heels together with the eyes open or closed. There was an intention tremor and incoordination in the right limbs in the finger-to-nose test and the heel-to-shin test. There was disorganization in alternating movement tests (dysdiadokokinesis) of the right hand. Sensory examination was normal


Explanation -

Cerebral cortical functions were normal. Cranial nerve involvement seemed absent except for the presence of nystagmus. In the Romberg test there was falling when the eyes were open or closed which might have signaled 8th nerve involvement but could also be a cerebellar sign. (A positive Romberg, falling after closing the eyes, indicates a posterior white column problem.) Muscle strength was nearly normal though the deep tendon reflexes and tone were decreased. The abnormal reflexes and tone are consistent with cerebellar disease. Intention tremor, abnormal finger-to-nose/heel-to-shin tests and broad-based gait on the right all indicate a right cerebellar lesion. Neurological signs appear on the same side as the lesion since the cerebellum functions largely ipsilaterally. Symptoms primarily in the limbs rather than the trunk suggest a cerebellar hemisphere rather than the vermis is involved.

The slow worsening suggests that the cause of the lesion is not vascular but is probably due to a tumor. The papilledema suggests a space taking phenomenon which also explains the headache and vomiting.

A cerebellar hemangioblastoma was discovered and removed.

Cerebellum Lesion - NEOPLASMS - TUMOR OF THE CEREBELLAR VERMIS

A Sample Case: A 6 year old was brought to the doctor because she was clumsy in walking and would sway and even topple over when seated. She also complained of nausea. Up to that point in time her growth and development was normal.

The neurological exam showed that she was alert and oriented with no signs of mental disturbance. There was papilledema. On attempting directed lateral gaze to either side the eyes showed horizontal oscillating movements. Cranial nerves were normal; motor strength and reflexes were normal as were all sensory systems.

When standing she was very unstable and would tumble to the left or right side. When seated she had trouble maintaining he head and torso in a stable vertical posture but if supported her finger-to-nose and heel-to-shin tests were nearly normal. When walking her gait was broad-based.


Explanation -

Mental status was normal and the cerebral hemispheres are intact. Cranial nerves are not involved and the sensory and motor systems are largely normal except for the truncal ataxia. The incoordinate movements in standing and sitting, walking, nystagmoid eye movements, are indicative of incoordination of the muscles of the trunk, i.e., truncal ataxia, which is controlled principally by the cerebellar vermis; lack of significant limb involvement suggests that the cerebellar hemispheres are not involved.

The headaches, long duration, and slow progression suggests a neoplasm rather than a vascular problem. Medulloblastoma is a common childhood malignancy which arises rapidly from the midline cerebellum to impact on the cerebellum, fills the 4th ventricle, and later affects the pons/medulla.

Basal Ganglia Lesion - VASCULAR - HEMORRHAGE IN THE SUBTHALAMIC NUCLEUS

A Sample Case:

A 50 yr old man was recovering well from motor and sensory deficits of his right arm and leg following a stroke which occurred 6 months earlier. There was no loss of language function. He became concerned when he began to experience sudden involuntary flinging movements of his right arm and leg which further interfered with walking and use of his arm. During sleep the abnormal movements ceased.

The patient was alert but had a long history of hypertension; upon examination, blood pressure, heart rate, and breathing rate were elevated. The cranial nerve exam was normal. Sudden flinging and writhing movements of the right arm and leg were forceful and of large amplitude and the arm showed bruises. Involuntary movements made testing strength and reflexes difficult but they appeared to be "normal" or at least consistent with the previous stroke.


Explanation -

The earlier stroke which created weakness and sensory loss of the right extremities is consistent with a left-sided lesion of the internal capsule or the cortex. Preservation of speech, involvement of both the arm and leg and normal cranial nerve functions suggests a lesion at the level of the posterior limb of the internal capsule rather that at the cortex.

The involuntary, sudden and violent swinging of the extremities, which disappears in sleep, on the right side is "ballism" and is associated with lesions of the left subthalamic nucleus. Symptoms of basal ganglia disease occur contralateral to the lesion because these extrapyramidal nuclei project (via the thalamus) to the ipsilateral motor cortical areas which give rise to the corticospinal tract which crosses in the medulla.

The sudden onset of unilateral deficits suggests that the cause is vascular rather than a degenerative process or a growing tumor. It would be reasonable to suggest that the initial stroke occurred in the subthalamic nucleus and that the nearby internal capsule was also effected. Recovery of strength and sensation from the limbs suggests that the internal capsule was impaired by edema which resolved without producing significant permanent damage. With the lifting of the paralysis then the ballistic movements resulting from injury to the subthalamic nucleus became evident. The blood supply to the subthalamic nucleus and the adjacent posterior limb of the internal capsule is by branches of the posterior communicating artery of the circle of Willis.