Thread: Neurology Clinical Cases

Medulla Lesion - VASCULAR LESIONS - LATERAL MEDULLARY SYNDROME (OF WALLENBERG)

A Sample Case: A 50 year old woman had a sudden onset of dizziness and vomiting. Her family noticed that her left eyelid appeared to be drooping and she was taken to see a doctor.

The neurologic exam demonstrated loss of pain and temperature sensation from her right side of the body but there was numbness on the left side of her face. Though there was normal proprioception and vibratory sensation bilaterally she still had an ataxic gait with falling toward the left side. There was no indication of spastic paralysis or Babinski signs. When she spoke her voice had a hoarse quality and she had a diminished gag reflex.


Explanation -

Dizziness and vomiting suggest a lesion above the spinal cord. Spinothalamic tract involvement on the left side is indicated by the loss of pain and temperature sensation from the right side of the body. Numbness of the face on the right is consistent with injury to the nucleus and tract of spinal V on the right side (which lies near the spinothalamic tracts). Hoarseness and an abnormal gag reflex indicates that the level of the lesion is that of CN IX and X. Normal proprioception and motor strength indicates intact medial lemniscus and pyramidal tracts; the ataxic gait is probably a "cerebellar" sign attributable to injury of the inferior cerebellar peduncle (which lies near the tract of spinal V and the spinothalamics).

Dizziness and vomiting may be due to involvement of the vestibular nuclei and/or CN X. Drooping of the right eyelid is part of the Horner's syndrome; at this level it is due to injury of the descending autonomics in the reticular formation.

The anatomic distribution of the involved structures indicates that the injury has occurred within the area of distribution of the posterior inferior cerebellar artery. Due to infarction, this is the most common medullary syndrome.

Medulla Lesion - VASCULAR LESIONS - MEDIAL MEDULLARY SYNDROME (INFERIOR ALTERNATING HEMIPLEGIA)

A Sample Case: A 63 year old woman suddenly fell to the floor and was unable to rise. She found that her left arm and leg were paralyzed and her speech was "thick".

Neurologic examination some months later showed that she had a spastic paralysis of her left limbs with increased tone and exaggerated deep tendon reflexes. Motor examination of the face was normal, however upon protrusion, the tongue pointed toward her right side; the right side of her tongue was atrophic.

The sensory exam indicated that pain and temperature was bilaterally normal from the body and face but there was loss of proprioception from the left lower extremity. Examination of other cranial nerves was normal.


Explanation -

Spastic paralysis of the left arm and leg indicates injury to the corticospinal tract somewhere along its length. The additional tongue signs places the corticospinal lesion above the cord, in the medulla, on the right side. The tongue usually points to the side of a lesion of the nucleus or fibers of CN XII. Atrophy of its muscles confirms a lower motor neuron lesion of the fibers of CN XII on the right side.

Loss of proprioception from the left lower extremity is consistent with injury to the ventral-most fibers of the medial lemniscus on the right side. Absence of other sensory findings limit the area of involvement to the distribution of the penetrating branches of the vertebral or anterior spinal artery, which include the pyramids, exiting fibers of CN XII, and the medial lemniscus.

Medulla Lesion - NEOPLASMS - MEDULLOBLASTOMA

A Sample Case: A boy 6 years of age was noticed by his mother as becoming increasingly listless. He complained of morning headaches. The child also began to vomit for no apparent reason. The mother at first thought that the child had some sort of stomach virus but it was his stumbling gait which made his mother seek medical advice.

The child was referred to a neurologist when the pediatrician discovered papilledema which signaled increased intracranial pressure. Examination revealed that the child had double vision and the eyes oscillated horizontally (nystagmus). There was a mild sensory loss and motor weakness on one side of the face. The child walked with a wide-based truncal ataxia. Radiologic imaging revealed 1) dilated lateral and 3rd ventricles and 2) a mass growing from the posterior part of the cerebellar vermis, filling the 4th ventricle and infiltrating its floor. Pathologic examination revealed a medulloblastoma which is considered an embryonic tumor arising from cells in the cerebellum.


Explanation -

The expanding tumor blocked the egress of cerebrospinal fluid from the ventricular system causing increased intracranial pressure, dilated ventricles, and headache. Pressure and/or infiltration by the malignant cells into the floor of the 4th ventricle impacted on nuclei of the vagus and vestibular nerves causing the vomiting and nystagmus. The broad-based gait and truncal ataxia is a sign of injury to the midline cerebellum (vermis). Interference with the nearby MLF and abducens nuclei would account for the diplopia; the asymmetrically expanding tumor has interfered with the descending tract of spinal V and the facial motor root producing the mild sensory and motor findings of the face

Pons Lesion - VASCULAR LESIONS - MEDIAL PONTINE SYNDROME (MIDDLE ALTERNATING HEMIPLEGIA)

A Sample Case: A 48 year old man suffered a sudden weakness of his left arm and leg which caused him to fall while shaving. He was helped to his feet but his left arm and leg felt stiff. In addition, he complained of seeing "double".

The neurologist found that the patient was alert with normal mental status. There was no evidence of increased intracranial pressure though his blood pressure was 200/95. There was a spastic paresis with a positive Babinski sign in the left extremities and loss of vibratory and positional sense on the left. The patient walked with an ataxic gait. Pain and temperature sensations were normal. There was diplopia when the patient looked toward the right side. At rest the right eye deviated toward the nose (internal strabismus or squint) while the left eye looked straight ahead. There was a paralysis of conjugate gaze toward the right, i.e, the right eye did not move laterally toward the right though the left eye did. Ocular convergence was normal.


Explanation -

The sudden onset suggests a lesion of vascular origin; the high blood pressure suggests the etiology. Though spastic paresis indicates involvement of the pyramidal tracts from the cerebrum on down, in this case, because of the 6th nerve injury at the level of the pons is indicated. In the pons the pyramidal tracts are in the basis pontis, and in this case the side opposite the weakness, i.e., the right side.

Ataxic gait, vibratory and positional deficits on the left suggest injury to the medial lemniscus, which lies near the midline in the ventral tegmentum, on the right. The ataxia could also have a cerebellar component due to injury of the basis pontis and the pontine nuclei. Normal pain and temperature perception indicate that the lesion was more limited to the midline rather than lateral where the spinothalamic and 5th nerve components lie.

Gaze paralysis to the right and internal strabismus of the right eye indicate weakness of the right lateral rectus and injury to the fibers of the right abducens nerve. If the 6th nucleus had been involved the medial rectus of the left eye would have shown signs as well, due to involvement of the nearby PPRF. Since convergence was preserved and only the lateral rectus of the right eye was paralyzed this was a lesion involving only the fibers of the 6th nerve.

This constellation of symptoms is consistent with the midline distribution of the paramedian branches of the basilar artery and occlusion of its branches in the caudal pons.

Pons Lesion - VASCULAR LESIONS - LATERAL INFERIOR PONTINE SYNDROME

A Sample Case: A 45 year old woman with a history of hypertension experienced a brief "blackout". She had complained of severe headaches, nausea, dizziness and a roaring sound in the left ear during the previous day. She also had difficulty walking and called a cab to take her to the hospital.

The physician found her mentally alert and communicative, the external auditory canals were clear and she was physically normal except for an elevated blood pressure of 165/105. Strength in her extremities was generally normal. Her speech was fluent and full of meaning though dysarthric. Nystagmus was present. There was a facial paralysis (upper and lower) on the left side which also had diminished sensation. There was impaired pain and temperature sense from the right side of the body. At rest, her eyes deviated toward the right; on command, there was paralysis of horizonal conjugate gaze to the left. Hearing was diminished on the left side. On the left, the eye drooped and the pupil was constricted.


Explanation -

Dizziness (vertigo), nausea and nystagmus can be the result of injury of the vestibular nerve or nucleus. The roaring sound (tinnitus) with diminished hearing on one side can be the result of injury to the cochlear nerve or nucleus on the left. Paralysis of the muscles of facial expression of the upper and lower face on the left results from injury of the left facial nerve or its motor nucleus. Diminished sensation on the left face suggests injury to the nearby descending tract and nucleus of spinal V. Diminished pain and temperature on the right side of the body is due to injury of the left spinothalamic tracts.

There was difficulty walking though motor strength was generally normal. This awkwardness may be attributable to injury of the left middle cerebellar peduncle. The drooping eyelid and constricted pupil suggest a Horner's syndrome due to injury of descending autonomic fibers in the lateral reticular formation.

The vestibulo-cochlear nerve/nuclei, the facial nerve/nucleus, tract/nucleus of spinal V, spinothalamic tract and middle cerebellar peduncle all lie laterally in the pons within the area of supply of the anterior inferior cerebellar artery.

Pons Lesion - VASCULAR LESIONS - MEDIAL MID-PONTINE SYNDROME

A Sample Case: A 55 year old man was brought to the hospital after suddenly falling to the ground unable to move his right arm and leg.

The neurologic exam revealed that the limbs on the right side had markedly diminished strength, heightened deep tendon reflexes, ankle clonus, positive Babinski and increased resistance to passive stretch. The left arm and leg had near normal strength but performed in an uncoordinated manner on the finger-to-nose test and the heel-to-shin test.

Cranial nerve examination was significant in that the upon smiling the man did not elevate his mouth on the right side and could not blow out his right cheek; he could tightly close his eyelids on both sides.


Explanation -

Occlusion of the paramedian branches of the mid-pontine basilar artery primarily injures the medial aspect of the basis pontis which carries the corticospinal, corticobulbar and corticopontine tracts. This results principally in motor symptoms which include paralysis of the lower face, spastic paresis and incoordination of the arms and legs on the side opposite the lesion. Incoordination without the spasticity on his right side is attributable to damage to cerebellar afferents. Pain and temperature sensation is usually normal although there may be impaired touch and proprioception contralaterally if the lesion extends deeply to the medial lemniscus.

Pons Lesion - VASCULAR LESIONS - LATERAL MID-PONTINE SYNDROME

A Sample Case: A 50 year old man developed an incoordination of his right hand and noticed while shaving that although he nicked the right side of his face that he felt no pain.

His general physical examination was basically normal. The principal findings of his neurologic exam revealed diminished pain and temperature sensation on the right side of his face and from the left side of his body. There was no corneal reflex closure of either eye in response to a wisp of cotton placed on the right cornea; there was a bilateral corneal response (blink) to cotton on the left cornea. The muscles of mastication were weak on the right and when asked to protrude his jaw it moved asymmetrically toward the right side. There was a diminished jaw jerk response.

Strength and muscle tone in his left arm and leg were normal but on the right side there was diminished tone, strength, and an intention tremor.


Explanation -

The loss of pain and temperature sensation on the right side of his face and left side of his body suggest injury to the spinothalamic tract on the right and the sensory division of CN 5 on the right side. The lack of a direct and consensual corneal response from stimulation of the eye on the right is also consistent with a 5th nerve sensory loss on the right. Motor weakness of the muscles of mastication, diminished jaw jerk and the pointing of the jaw to the right is consistent with injury to the motor fibers of the 5th nerve on the right; hence, both motor and sensory divisions of CN 5.

Motor examination indicated weakness and incoordination of the right arm and leg which is consistent with injury to the right cerebellar hemisphere or in this case the right middle cerebellar peduncle.

The short circumferential branches of the basilar artery at mid-pontine levels serve the middle cerebellar peduncle and in the tegmentum the motor and sensory root of the trigeminal nerve and the nearby spinothalamic tract.

Pons Lesion - VASCULAR LESIONS - MEDIAL SUPERIOR PONTINE SYNDROME

A Sample Case: A 60 year old man was suddenly stricken with paralysis of his right arm and leg. On reaching the hospital the major notable findings of the neurologic evaluation were spastic paresis of the right upper and lower extremities with increased deep tendon reflexes and a positive Babinski sign. The arm and leg on the left side performed in an ataxic manner on the finger-to-nose and heel-to-shin test but strength was normal. The muscles of the lips and cheeks were weak on the right side but the patient could tightly close both eyes and wrinkle his forehead symmetrically.

An internuclear ophthalmoplegia was observed in which the left eye would not adduct on attempted lateral gaze to the right although both eyes converged on near object. There was some loss of vibratory sense and discriminitive touch from the right arm.


Explanation -

The internuclear ophthalmoplegia helps to localize this lesion to the pons. On attempted lateral gaze to the right only the lateral rectus of the right eye functions; the medial rectus does not adduct the left eye. This would occur with lesions of the left medial longitudinal fasciculus (MLF) wherein the connection between the 6th and 3rd nerve for conjugate horizontal deviation is broken. Since both eyes converge it demonstrates that the 3rd nerves are intact (and that for convergence the pathway to the oculomotor nuclei does not involve the MLF).

The spastic paralysis of the arm, leg and only lower face on the right indicates injury to the upper motor neurons, i.e., corticospinal, corticobulbar tracts, on the left. On the left side there were ataxic cerebellar signs consistent with injury to the cerebellum on the right or, in this case the right basis pontis. Most of the upper motor neurons lie medially in the basis pontis.

In the area of the tegmentum, between the basis pontis containing the upper motor neurons and the MLF, lies the medial lemniscus. Injury to the medial aspect of the medial lemniscus would lead to loss of discriminative touch to the contralateral upper extremity.

The medial portion of the basis pontis and the MLF lie within the area of supply of the paramedian branches of the upper portion of the basilar artery.

Pons Lesion - NEOPLASMS - ACOUSTIC NEUROMA

A Sample Case: A 50 year old woman became aware that she could not feel the pressure of her mascara pencil on her right eyelid. She was already aware that her hearing was better on her left side than her right, from which she often was aware of a "ringing". She was troubled by a continuous sense of dizziness.

The neurologic exam confirmed that she had diminished hearing on the right side and upon questioning revealed that she suffered from headaches in addition to noting pain on the right side of her face. The woman had difficulty standing without swaying when her heels were together, whether her eyes were open or closed; her gait was slightly unsteady. She had a flat nasolabial fold on the right as well a weakness in wrinkling the forehead on that side. Nystagmus was elicited when looking to the right and she showed a loss of the right corneal reflex. Other cranial nerves and motor and sensory findings from arms, legs, and trunk were within normal limits. Radiologic imaging confirmed a diagnosis of acoustic neuroma in the cerebellopontine angle.


Explanation -

The tumor growing on the right 8th nerve produces auditory nerve irritation (ringing) and neuron death (deafness). Dizziness, nystagmus, nausea, and vomiting are signs of vestibular nerve involvement. Facial pain and loss of the corneal reflex on the right are also consistent with involvement of the sensory division of the 5th nerve on the right. Weakness of the muscles of the upper and lower face on the right implicates the motor division of the 7th nerve. Unsteadiness in standing and walking is attributable to involvement of the nearby cerebellar peduncles or the cerebellum. The evidence mostly indicates involvement of the peripheral divisions of the 5th, 7th and 8th cranial nerves and the cerebellum. This is a tumor derived by a overgrowth of Schwann cells originating on the vestibular nerve of the 8th nerve just within the internal auditory canal. As it grows the tumor extends into the posterior cranial fossa to the angle between the cerebellum and the pons. In this lateral position it compresses the 5th, 7th and, less often, the 9th and 10th cranial nerves.

Midbrain Lesion - VASCULAR LESIONS - SUPERIOR ALTERNATING HEMIPLEGIA (WEBER'S SYNDROME)

A Sample Case: A 55 year old woman had abdominal surgery 2 weeks before suddenly remarking to her husband that she was seeing double. She also felt a weakness in her left arm and leg. Her husband noticed that her right eyelid was drooping.

At the hospital she was awake, well oriented with normal memory. Her general physical condition was good. Her speech was articulate and the content was good. Her visual fields were normal but when asked to open her eyes the right eyelid did not open fully. When asked to look straight ahead the right eye was deviated to the right. On attempted lateral gaze to the left only the left eye responded. When asked to converge the eyes only the left eye was adducted and only the left eye showed pupillary constriction. Only the left eye constricted in response to light.

Upon smiling there was a minor weakness on the left. Her palate elevated symmetrically, gag reflex was normal, and corneal and jaw jerk responses were normal. The tongue protruded midline.

Motor strength was normal in the extremities on the right but was reduced on the left, especially in the arm where there was an increased biceps reflex and resistance to passive stretch.

Sensory examination was normal for the face and body on both sides.


Explanation -

The patient's complaint of weakness of the left arm and leg and the confirmation of spastic paresis, most marked in the upper extremity, indicates involvement of the corticospinal tract, either at high cervical levels of the cord on the left or somewhere above the cord on the right. The finding of cranial nerve signs (oculomotor) places the lesion above the cord on the right.

The major cranial nerve sign involves the fibers of the right oculomotor nerve. The cause of the patient's complaint of diplopia is explained by the neurologic exam wherein the right medial rectus muscle is paralyzed upon attempted lateral gaze to the left and in convergence. Vision in optic nerves was normal but there was failure of the right pupil to constrict to light or upon convergence. This indicates injury to the parasympathetic component of the 3rd nerve in addition to fibers supplying the extrinsic muscles of the eye and the eyelid. This places the lesion in the midbrain. The sensory examination was normal indicating that the tegmentum of the midbrain was spared. Except for an minor facial weakness cranial nerve motor functions were unaltered.

These symptoms place the lesion in the crus cerebri, probably more medially since the arm was more severely affected than the leg, where oculomotor fibers exit into the interpeduncular fossa. The sudden onset after abdominal surgery suggests a vascular infarct. The vessels supplying this area are the short penetrating paramedian branches of the basilar and posterior cerebral arteries.